| Message ID | 20210312200740.815014-1-danielhb413@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | DEVICE_NOT_DELETED/DEVICE_UNPLUG_ERROR QAPI events | expand |
On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > Hi, > > This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > Patches 1 and 3 are independent of the ppc patches and can be applied > separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > are dependent on the QAPI patches. Implementation looks fine, but I think there's a bit more to discuss before we can apply. I think it would make sense to re-order this and put UNPLUG_ERROR first. Its semantics are clearer, and I think there's a stronger case for it. I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does it really tell the user/management anything useful beyond what receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does?
On 3/22/21 10:12 PM, David Gibson wrote: > On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: >> Hi, >> >> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and >> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. >> >> Patches 1 and 3 are independent of the ppc patches and can be applied >> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and >> are dependent on the QAPI patches. > > Implementation looks fine, but I think there's a bit more to discuss > before we can apply. > > I think it would make sense to re-order this and put UNPLUG_ERROR > first. Its semantics are clearer, and I think there's a stronger case > for it. Alright > > I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > it really tell the user/management anything useful beyond what > receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? It informs that the hotunplug operation exceed the timeout that QEMU internals considers adequate, but QEMU can't assert that it was caused by an error or an unexpected delay. The end result is that the device is not going to be deleted from QMP, so DEVICE_NOT_DELETED. Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT event. Thanks, DHB >
On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > > On 3/22/21 10:12 PM, David Gibson wrote: > > On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > > Hi, > > > > > > This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > > DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > > > > > Patches 1 and 3 are independent of the ppc patches and can be applied > > > separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > > are dependent on the QAPI patches. > > > > Implementation looks fine, but I think there's a bit more to discuss > > before we can apply. > > > > I think it would make sense to re-order this and put UNPLUG_ERROR > > first. Its semantics are clearer, and I think there's a stronger case > > for it. > > Alright > > > > > I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > it really tell the user/management anything useful beyond what > > receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > > It informs that the hotunplug operation exceed the timeout that QEMU > internals considers adequate, but QEMU can't assert that it was caused > by an error or an unexpected delay. The end result is that the device > is not going to be deleted from QMP, so DEVICE_NOT_DELETED. Is it, though? I mean, it is with this implementation for papr: because we clear the unplug_requested flag, even if the guest later tries to complete the unplug, it will fail. But if I understand what Markus was saying correctly, that might not be possible for all hotplug systems. I believe Markus was suggesting that DEVICE_NOT_DELETED could just mean that we haven't deleted the device yet, but it could still happen later. And in that case, I'm not yet sold on the value of a message that essentially just means "Ayup, still dunno what's happening, sorry". > Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > event. Hm... what if we added a "reason" field to UNPLUG_ERROR. That could be "guest rejected hotplug", or something more specific, in the rare case that the guest has a way of signalling something more specific, or "timeout" - but the later *only* to be sent in cases where on the timeout we're able to block any later completion of the unplug (as we can on papr). Thoughs, Markus?
On 3/23/21 10:40 PM, David Gibson wrote: > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: >> >> >> On 3/22/21 10:12 PM, David Gibson wrote: >>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: >>>> Hi, >>>> >>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and >>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. >>>> >>>> Patches 1 and 3 are independent of the ppc patches and can be applied >>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and >>>> are dependent on the QAPI patches. >>> >>> Implementation looks fine, but I think there's a bit more to discuss >>> before we can apply. >>> >>> I think it would make sense to re-order this and put UNPLUG_ERROR >>> first. Its semantics are clearer, and I think there's a stronger case >>> for it. >> >> Alright >> >>> >>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does >>> it really tell the user/management anything useful beyond what >>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? >> >> >> It informs that the hotunplug operation exceed the timeout that QEMU >> internals considers adequate, but QEMU can't assert that it was caused >> by an error or an unexpected delay. The end result is that the device >> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > Is it, though? I mean, it is with this implementation for papr: > because we clear the unplug_requested flag, even if the guest later > tries to complete the unplug, it will fail. > > But if I understand what Markus was saying correctly, that might not > be possible for all hotplug systems. I believe Markus was suggesting > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > device yet, but it could still happen later. > > And in that case, I'm not yet sold on the value of a message that > essentially just means "Ayup, still dunno what's happening, sorry". > >> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT >> event. > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > be "guest rejected hotplug", or something more specific, in the rare > case that the guest has a way of signalling something more specific, > or "timeout" - but the later *only* to be sent in cases where on the > timeout we're able to block any later completion of the unplug (as we > can on papr). I believe that's already covered by the existing API: +# @DEVICE_UNPLUG_ERROR: +# +# Emitted when a device hot unplug error occurs. +# +# @device: device name +# +# @msg: Informative message The 'informative message' would be the reason the event occurred. In patch 4/4, for the memory hotunplug refused by the guest, it is being set as: qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " "for device %s", dev->id); qapi_event_send_device_unplug_error(dev->id, qapi_error); We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout case (currently on patch 2/4) by just changing 'msg', e.g.: qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); qapi_event_send_device_unplug_error(dev->id, qapi_error); Thanks, DHB > > Thoughs, Markus? >
On Wed, Mar 24, 2021 at 04:09:59PM -0300, Daniel Henrique Barboza wrote: > > > On 3/23/21 10:40 PM, David Gibson wrote: > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > > > > > > > > On 3/22/21 10:12 PM, David Gibson wrote: > > > > On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > > > > Hi, > > > > > > > > > > This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > > > > DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > > > > > > > > > Patches 1 and 3 are independent of the ppc patches and can be applied > > > > > separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > > > > are dependent on the QAPI patches. > > > > > > > > Implementation looks fine, but I think there's a bit more to discuss > > > > before we can apply. > > > > > > > > I think it would make sense to re-order this and put UNPLUG_ERROR > > > > first. Its semantics are clearer, and I think there's a stronger case > > > > for it. > > > > > > Alright > > > > > > > > > > > I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > > > it really tell the user/management anything useful beyond what > > > > receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > > > > > > > > It informs that the hotunplug operation exceed the timeout that QEMU > > > internals considers adequate, but QEMU can't assert that it was caused > > > by an error or an unexpected delay. The end result is that the device > > > is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > Is it, though? I mean, it is with this implementation for papr: > > because we clear the unplug_requested flag, even if the guest later > > tries to complete the unplug, it will fail. > > > > But if I understand what Markus was saying correctly, that might not > > be possible for all hotplug systems. I believe Markus was suggesting > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > device yet, but it could still happen later. > > > > And in that case, I'm not yet sold on the value of a message that > > essentially just means "Ayup, still dunno what's happening, sorry". > > > > > Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > > > event. > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > be "guest rejected hotplug", or something more specific, in the rare > > case that the guest has a way of signalling something more specific, > > or "timeout" - but the later *only* to be sent in cases where on the > > timeout we're able to block any later completion of the unplug (as we > > can on papr). > > I believe that's already covered by the existing API: > > > +# @DEVICE_UNPLUG_ERROR: > +# > +# Emitted when a device hot unplug error occurs. > +# > +# @device: device name > +# > +# @msg: Informative message Oh, sorry, I missed that > The 'informative message' would be the reason the event occurred. In patch > 4/4, for the memory hotunplug refused by the guest, it is being set as: > > qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " > "for device %s", dev->id); > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout > case (currently on patch 2/4) by just changing 'msg', e.g.: > > > qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); > qapi_event_send_device_unplug_error(dev->id, qapi_error); I think that makes sense for the cases on papr. Less sure about the cases Markus has mentioned.
On Wed, 24 Mar 2021 16:09:59 -0300 Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > On 3/23/21 10:40 PM, David Gibson wrote: > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > >> > >> > >> On 3/22/21 10:12 PM, David Gibson wrote: > >>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > >>>> Hi, > >>>> > >>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > >>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > >>>> > >>>> Patches 1 and 3 are independent of the ppc patches and can be applied > >>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > >>>> are dependent on the QAPI patches. > >>> > >>> Implementation looks fine, but I think there's a bit more to discuss > >>> before we can apply. > >>> > >>> I think it would make sense to re-order this and put UNPLUG_ERROR > >>> first. Its semantics are clearer, and I think there's a stronger case > >>> for it. > >> > >> Alright > >> > >>> > >>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > >>> it really tell the user/management anything useful beyond what > >>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > >> > >> > >> It informs that the hotunplug operation exceed the timeout that QEMU > >> internals considers adequate, but QEMU can't assert that it was caused > >> by an error or an unexpected delay. The end result is that the device > >> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > Is it, though? I mean, it is with this implementation for papr: > > because we clear the unplug_requested flag, even if the guest later > > tries to complete the unplug, it will fail. > > > > But if I understand what Markus was saying correctly, that might not > > be possible for all hotplug systems. I believe Markus was suggesting > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > device yet, but it could still happen later. > > > > And in that case, I'm not yet sold on the value of a message that > > essentially just means "Ayup, still dunno what's happening, sorry". > > > >> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > >> event. > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > be "guest rejected hotplug", or something more specific, in the rare > > case that the guest has a way of signalling something more specific, > > or "timeout" - but the later *only* to be sent in cases where on the > > timeout we're able to block any later completion of the unplug (as we > > can on papr). Is canceling unplug on timeout documented somewhere (like some spec)? If not it might (theoretically) confuse guest when it tries to unplug after timeout and leave guest in some unexpected state. > > I believe that's already covered by the existing API: > > > +# @DEVICE_UNPLUG_ERROR: > +# > +# Emitted when a device hot unplug error occurs. > +# > +# @device: device name > +# > +# @msg: Informative message > > The 'informative message' would be the reason the event occurred. In patch > 4/4, for the memory hotunplug refused by the guest, it is being set as: > > qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " > "for device %s", dev->id); > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout > case (currently on patch 2/4) by just changing 'msg', e.g.: > > > qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); > qapi_event_send_device_unplug_error(dev->id, qapi_error); > lets make everything support ACPI (just kidding). maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR which sort of does the same thing (and more) but instead of strings uses status codes defined by spec. Idea similar to DEVICE_UNPLUG_ERROR was considered back then, but instead of QEMU being a poor translator of status codes to non machine-readable strings we went with exposing well documented status codes to user. This way user can implement specific reactions to particular errors just looking at JSON + spec. > Thanks, > > DHB > > > > > > Thoughs, Markus? > > >
On Tue, Mar 30, 2021 at 01:28:31AM +0200, Igor Mammedov wrote: > On Wed, 24 Mar 2021 16:09:59 -0300 > Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > > > On 3/23/21 10:40 PM, David Gibson wrote: > > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > >> > > >> > > >> On 3/22/21 10:12 PM, David Gibson wrote: > > >>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > >>>> Hi, > > >>>> > > >>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > >>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > >>>> > > >>>> Patches 1 and 3 are independent of the ppc patches and can be applied > > >>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > >>>> are dependent on the QAPI patches. > > >>> > > >>> Implementation looks fine, but I think there's a bit more to discuss > > >>> before we can apply. > > >>> > > >>> I think it would make sense to re-order this and put UNPLUG_ERROR > > >>> first. Its semantics are clearer, and I think there's a stronger case > > >>> for it. > > >> > > >> Alright > > >> > > >>> > > >>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > >>> it really tell the user/management anything useful beyond what > > >>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > >> > > >> > > >> It informs that the hotunplug operation exceed the timeout that QEMU > > >> internals considers adequate, but QEMU can't assert that it was caused > > >> by an error or an unexpected delay. The end result is that the device > > >> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > > > Is it, though? I mean, it is with this implementation for papr: > > > because we clear the unplug_requested flag, even if the guest later > > > tries to complete the unplug, it will fail. > > > > > > But if I understand what Markus was saying correctly, that might not > > > be possible for all hotplug systems. I believe Markus was suggesting > > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > > device yet, but it could still happen later. > > > > > > And in that case, I'm not yet sold on the value of a message that > > > essentially just means "Ayup, still dunno what's happening, sorry". > > > > > >> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > > >> event. > > > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > > be "guest rejected hotplug", or something more specific, in the rare > > > case that the guest has a way of signalling something more specific, > > > or "timeout" - but the later *only* to be sent in cases where on the > > > timeout we're able to block any later completion of the unplug (as we > > > can on papr). > > Is canceling unplug on timeout documented somewhere (like some spec)? Uh.. not as such. In the PAPR model, hotplugs and unplugs are mostly guest directed, so the question doesn't really arise. > If not it might (theoretically) confuse guest when it tries to unplug > after timeout and leave guest in some unexpected state. Possible, but probably not that likely. The mechanism we use to "cancel" the hotplugs is that we just fail the hypercalls that the guest will need to call to actually complete the hotplug. We also fail those in some other situations, and that seems to work. That said, I no longer think this cancelling on timeout is a good idea, since it mismatches what happens on other platforms more than I think we need to. My now preferred approach is to revert the timeout changes, but instead allow retries of unplugs to be issued. I think that's just a matter of resending the unplug message to the guest, while making it otherwise a no-op on the qemu side. > > I believe that's already covered by the existing API: > > > > > > +# @DEVICE_UNPLUG_ERROR: > > +# > > +# Emitted when a device hot unplug error occurs. > > +# > > +# @device: device name > > +# > > +# @msg: Informative message > > > > The 'informative message' would be the reason the event occurred. In patch > > 4/4, for the memory hotunplug refused by the guest, it is being set as: > > > > qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " > > "for device %s", dev->id); > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > > > > > We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout > > case (currently on patch 2/4) by just changing 'msg', e.g.: > > > > > > qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > lets make everything support ACPI (just kidding). Heh. If nothing else, doesn't help us with existing guests. > maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR > which sort of does the same thing (and more) but instead of strings uses status codes > defined by spec. Hmm. I'm a bit dubious about issuing ACPI messages for a non ACPI guest, but maybe that could work. > Idea similar to DEVICE_UNPLUG_ERROR was considered back then, but instead of QEMU being > a poor translator of status codes to non machine-readable strings we went with > exposing well documented status codes to user. This way user can implement > specific reactions to particular errors just looking at JSON + spec. > > > Thanks, > > > > DHB > > > > > > > > > > Thoughs, Markus? > > > > > >
On Wed, 31 Mar 2021 10:46:49 +1100 David Gibson <david@gibson.dropbear.id.au> wrote: > On Tue, Mar 30, 2021 at 01:28:31AM +0200, Igor Mammedov wrote: > > On Wed, 24 Mar 2021 16:09:59 -0300 > > Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > > > > > On 3/23/21 10:40 PM, David Gibson wrote: > > > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > > >> > > > >> > > > >> On 3/22/21 10:12 PM, David Gibson wrote: > > > >>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > > >>>> Hi, > > > >>>> > > > >>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > > >>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > > >>>> > > > >>>> Patches 1 and 3 are independent of the ppc patches and can be applied > > > >>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > > >>>> are dependent on the QAPI patches. > > > >>> > > > >>> Implementation looks fine, but I think there's a bit more to discuss > > > >>> before we can apply. > > > >>> > > > >>> I think it would make sense to re-order this and put UNPLUG_ERROR > > > >>> first. Its semantics are clearer, and I think there's a stronger case > > > >>> for it. > > > >> > > > >> Alright > > > >> > > > >>> > > > >>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > > >>> it really tell the user/management anything useful beyond what > > > >>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > > >> > > > >> > > > >> It informs that the hotunplug operation exceed the timeout that QEMU > > > >> internals considers adequate, but QEMU can't assert that it was caused > > > >> by an error or an unexpected delay. The end result is that the device > > > >> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > > > > > Is it, though? I mean, it is with this implementation for papr: > > > > because we clear the unplug_requested flag, even if the guest later > > > > tries to complete the unplug, it will fail. > > > > > > > > But if I understand what Markus was saying correctly, that might not > > > > be possible for all hotplug systems. I believe Markus was suggesting > > > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > > > device yet, but it could still happen later. > > > > > > > > And in that case, I'm not yet sold on the value of a message that > > > > essentially just means "Ayup, still dunno what's happening, sorry". > > > > > > > >> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > > > >> event. > > > > > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > > > be "guest rejected hotplug", or something more specific, in the rare > > > > case that the guest has a way of signalling something more specific, > > > > or "timeout" - but the later *only* to be sent in cases where on the > > > > timeout we're able to block any later completion of the unplug (as we > > > > can on papr). > > > > Is canceling unplug on timeout documented somewhere (like some spec)? > > Uh.. not as such. In the PAPR model, hotplugs and unplugs are mostly > guest directed, so the question doesn't really arise. > > > If not it might (theoretically) confuse guest when it tries to unplug > > after timeout and leave guest in some unexpected state. > > Possible, but probably not that likely. The mechanism we use to > "cancel" the hotplugs is that we just fail the hypercalls that the > guest will need to call to actually complete the hotplug. We also > fail those in some other situations, and that seems to work. > > That said, I no longer think this cancelling on timeout is a good > idea, since it mismatches what happens on other platforms more than I > think we need to. > > My now preferred approach is to revert the timeout changes, but > instead allow retries of unplugs to be issued. I think that's just a > matter of resending the unplug message to the guest, while making it > otherwise a no-op on the qemu side. Yep, all we need to do is notify QEMU user, so it knows that unplug has failed. Then It can decide on it's own what to do with it and also when. > > > I believe that's already covered by the existing API: > > > > > > > > > +# @DEVICE_UNPLUG_ERROR: > > > +# > > > +# Emitted when a device hot unplug error occurs. > > > +# > > > +# @device: device name > > > +# > > > +# @msg: Informative message > > > > > > The 'informative message' would be the reason the event occurred. In patch > > > 4/4, for the memory hotunplug refused by the guest, it is being set as: > > > > > > qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " > > > "for device %s", dev->id); > > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > > > > > > > > > We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout > > > case (currently on patch 2/4) by just changing 'msg', e.g.: > > > > > > > > > qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); > > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > > > > lets make everything support ACPI (just kidding). > > Heh. If nothing else, doesn't help us with existing guests. > > > maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR > > which sort of does the same thing (and more) but instead of strings uses status codes > > defined by spec. > > Hmm. I'm a bit dubious about issuing ACPI messages for a non ACPI > guest, but maybe that could work. May be we can rename it to be ACPI agnostic (though I'm not sure how renaming QAPI interfaces should be done (it might upset libvirt for example)). (My point was that ACPI spec had already gone through all the trouble defining status of completion and documenting it. Also libvirt supports this notification. It looks like worthwhile thing to consider if can somehow reuse it outside of x86 world) > > Idea similar to DEVICE_UNPLUG_ERROR was considered back then, but instead of QEMU being > > a poor translator of status codes to non machine-readable strings we went with > > exposing well documented status codes to user. This way user can implement > > specific reactions to particular errors just looking at JSON + spec. > > > > > Thanks, > > > > > > DHB > > > > > > > > > > > > > > Thoughs, Markus? > > > > > > > > > >
On 3/29/21 8:28 PM, Igor Mammedov wrote: > On Wed, 24 Mar 2021 16:09:59 -0300 > Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > >> On 3/23/21 10:40 PM, David Gibson wrote: >>> On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: >>>> >>>> >>>> On 3/22/21 10:12 PM, David Gibson wrote: >>>>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: >>>>>> Hi, >>>>>> >>>>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and >>>>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. >>>>>> >>>>>> Patches 1 and 3 are independent of the ppc patches and can be applied >>>>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and >>>>>> are dependent on the QAPI patches. >>>>> >>>>> Implementation looks fine, but I think there's a bit more to discuss >>>>> before we can apply. >>>>> >>>>> I think it would make sense to re-order this and put UNPLUG_ERROR >>>>> first. Its semantics are clearer, and I think there's a stronger case >>>>> for it. >>>> >>>> Alright >>>> >>>>> >>>>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does >>>>> it really tell the user/management anything useful beyond what >>>>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? >>>> >>>> >>>> It informs that the hotunplug operation exceed the timeout that QEMU >>>> internals considers adequate, but QEMU can't assert that it was caused >>>> by an error or an unexpected delay. The end result is that the device >>>> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. >>> >>> Is it, though? I mean, it is with this implementation for papr: >>> because we clear the unplug_requested flag, even if the guest later >>> tries to complete the unplug, it will fail. >>> >>> But if I understand what Markus was saying correctly, that might not >>> be possible for all hotplug systems. I believe Markus was suggesting >>> that DEVICE_NOT_DELETED could just mean that we haven't deleted the >>> device yet, but it could still happen later. >>> >>> And in that case, I'm not yet sold on the value of a message that >>> essentially just means "Ayup, still dunno what's happening, sorry". >>> >>>> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT >>>> event. >>> >>> Hm... what if we added a "reason" field to UNPLUG_ERROR. That could >>> be "guest rejected hotplug", or something more specific, in the rare >>> case that the guest has a way of signalling something more specific, >>> or "timeout" - but the later *only* to be sent in cases where on the >>> timeout we're able to block any later completion of the unplug (as we >>> can on papr). > > Is canceling unplug on timeout documented somewhere (like some spec)? Nope. > > If not it might (theoretically) confuse guest when it tries to unplug > after timeout and leave guest in some unexpected state. I consider this a remote possibility due to the generous timeout we're using in the machine, but it is a possibility nevertheless. > >> >> I believe that's already covered by the existing API: >> >> >> +# @DEVICE_UNPLUG_ERROR: >> +# >> +# Emitted when a device hot unplug error occurs. >> +# >> +# @device: device name >> +# >> +# @msg: Informative message >> >> The 'informative message' would be the reason the event occurred. In patch >> 4/4, for the memory hotunplug refused by the guest, it is being set as: >> >> qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " >> "for device %s", dev->id); >> qapi_event_send_device_unplug_error(dev->id, qapi_error); >> >> >> >> We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout >> case (currently on patch 2/4) by just changing 'msg', e.g.: >> >> >> qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); >> qapi_event_send_device_unplug_error(dev->id, qapi_error); >> > > lets make everything support ACPI (just kidding). I would love to make PAPR more ACPI and less .... PAPR. > > maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR > which sort of does the same thing (and more) but instead of strings uses status codes > defined by spec. > > Idea similar to DEVICE_UNPLUG_ERROR was considered back then, but instead of QEMU being > a poor translator of status codes to non machine-readable strings we went with > exposing well documented status codes to user. This way user can implement > specific reactions to particular errors just looking at JSON + spec. This is not a bad idea. Problem is that we don't have all ACPI_DEVICE_OST fields to fill in because, well, both the timeout and the cancell mechanism aren't specified there. Thanks, DHB > >> Thanks, >> >> DHB >> >> >>> >>> Thoughs, Markus? >>> >> >
On 3/30/21 8:46 PM, David Gibson wrote: > On Tue, Mar 30, 2021 at 01:28:31AM +0200, Igor Mammedov wrote: >> On Wed, 24 Mar 2021 16:09:59 -0300 >> Daniel Henrique Barboza <danielhb413@gmail.com> wrote: >> >>> On 3/23/21 10:40 PM, David Gibson wrote: >>>> On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: >>>>> >>>>> >>>>> On 3/22/21 10:12 PM, David Gibson wrote: >>>>>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: >>>>>>> Hi, >>>>>>> >>>>>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and >>>>>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. >>>>>>> >>>>>>> Patches 1 and 3 are independent of the ppc patches and can be applied >>>>>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and >>>>>>> are dependent on the QAPI patches. >>>>>> >>>>>> Implementation looks fine, but I think there's a bit more to discuss >>>>>> before we can apply. >>>>>> >>>>>> I think it would make sense to re-order this and put UNPLUG_ERROR >>>>>> first. Its semantics are clearer, and I think there's a stronger case >>>>>> for it. >>>>> >>>>> Alright >>>>> >>>>>> >>>>>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does >>>>>> it really tell the user/management anything useful beyond what >>>>>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? >>>>> >>>>> >>>>> It informs that the hotunplug operation exceed the timeout that QEMU >>>>> internals considers adequate, but QEMU can't assert that it was caused >>>>> by an error or an unexpected delay. The end result is that the device >>>>> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. >>>> >>>> Is it, though? I mean, it is with this implementation for papr: >>>> because we clear the unplug_requested flag, even if the guest later >>>> tries to complete the unplug, it will fail. >>>> >>>> But if I understand what Markus was saying correctly, that might not >>>> be possible for all hotplug systems. I believe Markus was suggesting >>>> that DEVICE_NOT_DELETED could just mean that we haven't deleted the >>>> device yet, but it could still happen later. >>>> >>>> And in that case, I'm not yet sold on the value of a message that >>>> essentially just means "Ayup, still dunno what's happening, sorry". >>>> >>>>> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT >>>>> event. >>>> >>>> Hm... what if we added a "reason" field to UNPLUG_ERROR. That could >>>> be "guest rejected hotplug", or something more specific, in the rare >>>> case that the guest has a way of signalling something more specific, >>>> or "timeout" - but the later *only* to be sent in cases where on the >>>> timeout we're able to block any later completion of the unplug (as we >>>> can on papr). >> >> Is canceling unplug on timeout documented somewhere (like some spec)? > > Uh.. not as such. In the PAPR model, hotplugs and unplugs are mostly > guest directed, so the question doesn't really arise. > >> If not it might (theoretically) confuse guest when it tries to unplug >> after timeout and leave guest in some unexpected state. > > Possible, but probably not that likely. The mechanism we use to > "cancel" the hotplugs is that we just fail the hypercalls that the > guest will need to call to actually complete the hotplug. We also > fail those in some other situations, and that seems to work. > > That said, I no longer think this cancelling on timeout is a good > idea, since it mismatches what happens on other platforms more than I > think we need to. > > My now preferred approach is to revert the timeout changes, but > instead allow retries of unplugs to be issued. I think that's just a > matter of resending the unplug message to the guest, while making it > otherwise a no-op on the qemu side. I used this approach in a patch I sent back in January: "[PATCH v2 1/1] spapr.c: always pulse guest IRQ in spapr_core_unplug_request()" https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04399.html Let me know and I'll revert the timeout mechanism and re-post this one. I guess there's still time to make this change in the 6.0.0 window, avoiding releasing a mechanism we're not happy with. Thanks, DHB > >>> I believe that's already covered by the existing API: >>> >>> >>> +# @DEVICE_UNPLUG_ERROR: >>> +# >>> +# Emitted when a device hot unplug error occurs. >>> +# >>> +# @device: device name >>> +# >>> +# @msg: Informative message >>> >>> The 'informative message' would be the reason the event occurred. In patch >>> 4/4, for the memory hotunplug refused by the guest, it is being set as: >>> >>> qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " >>> "for device %s", dev->id); >>> qapi_event_send_device_unplug_error(dev->id, qapi_error); >>> >>> >>> >>> We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout >>> case (currently on patch 2/4) by just changing 'msg', e.g.: >>> >>> >>> qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); >>> qapi_event_send_device_unplug_error(dev->id, qapi_error); >>> >> >> lets make everything support ACPI (just kidding). > > Heh. If nothing else, doesn't help us with existing guests. > >> maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR >> which sort of does the same thing (and more) but instead of strings uses status codes >> defined by spec. > > Hmm. I'm a bit dubious about issuing ACPI messages for a non ACPI > guest, but maybe that could work. > >> Idea similar to DEVICE_UNPLUG_ERROR was considered back then, but instead of QEMU being >> a poor translator of status codes to non machine-readable strings we went with >> exposing well documented status codes to user. This way user can implement >> specific reactions to particular errors just looking at JSON + spec. >> >>> Thanks, >>> >>> DHB >>> >>> >>>> >>>> Thoughs, Markus? >>>> >>> >> >
On Wed, Mar 31, 2021 at 11:49:14AM +0200, Igor Mammedov wrote: > On Wed, 31 Mar 2021 10:46:49 +1100 > David Gibson <david@gibson.dropbear.id.au> wrote: > > > On Tue, Mar 30, 2021 at 01:28:31AM +0200, Igor Mammedov wrote: > > > On Wed, 24 Mar 2021 16:09:59 -0300 > > > Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > > > > > > > On 3/23/21 10:40 PM, David Gibson wrote: > > > > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > > > >> > > > > >> > > > > >> On 3/22/21 10:12 PM, David Gibson wrote: > > > > >>> On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > > > >>>> Hi, > > > > >>>> > > > > >>>> This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > > > >>>> DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > > > >>>> > > > > >>>> Patches 1 and 3 are independent of the ppc patches and can be applied > > > > >>>> separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > > > >>>> are dependent on the QAPI patches. > > > > >>> > > > > >>> Implementation looks fine, but I think there's a bit more to discuss > > > > >>> before we can apply. > > > > >>> > > > > >>> I think it would make sense to re-order this and put UNPLUG_ERROR > > > > >>> first. Its semantics are clearer, and I think there's a stronger case > > > > >>> for it. > > > > >> > > > > >> Alright > > > > >> > > > > >>> > > > > >>> I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > > > >>> it really tell the user/management anything useful beyond what > > > > >>> receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > > > >> > > > > >> > > > > >> It informs that the hotunplug operation exceed the timeout that QEMU > > > > >> internals considers adequate, but QEMU can't assert that it was caused > > > > >> by an error or an unexpected delay. The end result is that the device > > > > >> is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > > > > > > > Is it, though? I mean, it is with this implementation for papr: > > > > > because we clear the unplug_requested flag, even if the guest later > > > > > tries to complete the unplug, it will fail. > > > > > > > > > > But if I understand what Markus was saying correctly, that might not > > > > > be possible for all hotplug systems. I believe Markus was suggesting > > > > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > > > > device yet, but it could still happen later. > > > > > > > > > > And in that case, I'm not yet sold on the value of a message that > > > > > essentially just means "Ayup, still dunno what's happening, sorry". > > > > > > > > > >> Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > > > > >> event. > > > > > > > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > > > > be "guest rejected hotplug", or something more specific, in the rare > > > > > case that the guest has a way of signalling something more specific, > > > > > or "timeout" - but the later *only* to be sent in cases where on the > > > > > timeout we're able to block any later completion of the unplug (as we > > > > > can on papr). > > > > > > Is canceling unplug on timeout documented somewhere (like some spec)? > > > > Uh.. not as such. In the PAPR model, hotplugs and unplugs are mostly > > guest directed, so the question doesn't really arise. > > > > > If not it might (theoretically) confuse guest when it tries to unplug > > > after timeout and leave guest in some unexpected state. > > > > Possible, but probably not that likely. The mechanism we use to > > "cancel" the hotplugs is that we just fail the hypercalls that the > > guest will need to call to actually complete the hotplug. We also > > fail those in some other situations, and that seems to work. > > > > That said, I no longer think this cancelling on timeout is a good > > idea, since it mismatches what happens on other platforms more than I > > think we need to. > > > > My now preferred approach is to revert the timeout changes, but > > instead allow retries of unplugs to be issued. I think that's just a > > matter of resending the unplug message to the guest, while making it > > otherwise a no-op on the qemu side. > > Yep, all we need to do is notify QEMU user, so it knows that unplug > has failed. Then It can decide on it's own what to do with it and also when. I'm not sure even that makes sense. I mean in the cases that the guest specifically signals failure, then yes, we should definitely notify the user. But for the cases the timeout was covering, I'm not convinced a notification is useful: we *don't* know the unplug has failed, we only suspect it, and I don't see that qemu really has any more information than the user about what the expected time for an unplug should be. > > > > I believe that's already covered by the existing API: > > > > > > > > > > > > +# @DEVICE_UNPLUG_ERROR: > > > > +# > > > > +# Emitted when a device hot unplug error occurs. > > > > +# > > > > +# @device: device name > > > > +# > > > > +# @msg: Informative message > > > > > > > > The 'informative message' would be the reason the event occurred. In patch > > > > 4/4, for the memory hotunplug refused by the guest, it is being set as: > > > > > > > > qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " > > > > "for device %s", dev->id); > > > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > > > > > > > > > > > > > We could use the same DEVICE_UNPLUG_ERROR event in the CPU hotunplug timeout > > > > case (currently on patch 2/4) by just changing 'msg', e.g.: > > > > > > > > > > > > qapi_error = g_strdup_printf("CPU hotunplug timeout for device %s", dev->id); > > > > qapi_event_send_device_unplug_error(dev->id, qapi_error); > > > > > > > > > > lets make everything support ACPI (just kidding). > > > > Heh. If nothing else, doesn't help us with existing guests. > > > > > maybe we can reuse already existing ACPI_DEVICE_OST instead of DEVICE_UNPLUG_ERROR > > > which sort of does the same thing (and more) but instead of strings uses status codes > > > defined by spec. > > > > Hmm. I'm a bit dubious about issuing ACPI messages for a non ACPI > > guest, but maybe that could work. > > May be we can rename it to be ACPI agnostic (though I'm not sure how renaming > QAPI interfaces should be done (it might upset libvirt for example)). > > (My point was that ACPI spec had already gone through all the trouble defining > status of completion and documenting it. Also libvirt supports this notification. > It looks like worthwhile thing to consider if can somehow reuse it outside of > x86 world) Yeah, that's a fair point.
On Wed, Mar 31, 2021 at 04:47:14PM -0300, Daniel Henrique Barboza wrote: > > > On 3/30/21 8:46 PM, David Gibson wrote: > > On Tue, Mar 30, 2021 at 01:28:31AM +0200, Igor Mammedov wrote: > > > On Wed, 24 Mar 2021 16:09:59 -0300 > > > Daniel Henrique Barboza <danielhb413@gmail.com> wrote: > > > > > > > On 3/23/21 10:40 PM, David Gibson wrote: > > > > > On Tue, Mar 23, 2021 at 02:10:22PM -0300, Daniel Henrique Barboza wrote: > > > > > > > > > > > > > > > > > > On 3/22/21 10:12 PM, David Gibson wrote: > > > > > > > On Fri, Mar 12, 2021 at 05:07:36PM -0300, Daniel Henrique Barboza wrote: > > > > > > > > Hi, > > > > > > > > > > > > > > > > This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > > > > > > > > DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > > > > > > > > > > > > > > > Patches 1 and 3 are independent of the ppc patches and can be applied > > > > > > > > separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > > > > > > > > are dependent on the QAPI patches. > > > > > > > > > > > > > > Implementation looks fine, but I think there's a bit more to discuss > > > > > > > before we can apply. > > > > > > > > > > > > > > I think it would make sense to re-order this and put UNPLUG_ERROR > > > > > > > first. Its semantics are clearer, and I think there's a stronger case > > > > > > > for it. > > > > > > > > > > > > Alright > > > > > > > > > > > > > > I'm a bit less sold on DEVICE_NOT_DELETED, after consideration. Does > > > > > > > it really tell the user/management anything useful beyond what > > > > > > > receiving neither a DEVICE_DELETED nor a DEVICE_UNPLUG_ERROR does? > > > > > > > > > > > > > > > > > > It informs that the hotunplug operation exceed the timeout that QEMU > > > > > > internals considers adequate, but QEMU can't assert that it was caused > > > > > > by an error or an unexpected delay. The end result is that the device > > > > > > is not going to be deleted from QMP, so DEVICE_NOT_DELETED. > > > > > > > > > > Is it, though? I mean, it is with this implementation for papr: > > > > > because we clear the unplug_requested flag, even if the guest later > > > > > tries to complete the unplug, it will fail. > > > > > > > > > > But if I understand what Markus was saying correctly, that might not > > > > > be possible for all hotplug systems. I believe Markus was suggesting > > > > > that DEVICE_NOT_DELETED could just mean that we haven't deleted the > > > > > device yet, but it could still happen later. > > > > > > > > > > And in that case, I'm not yet sold on the value of a message that > > > > > essentially just means "Ayup, still dunno what's happening, sorry". > > > > > > Perhaps we should just be straightforward and create a DEVICE_UNPLUG_TIMEOUT > > > > > > event. > > > > > > > > > > Hm... what if we added a "reason" field to UNPLUG_ERROR. That could > > > > > be "guest rejected hotplug", or something more specific, in the rare > > > > > case that the guest has a way of signalling something more specific, > > > > > or "timeout" - but the later *only* to be sent in cases where on the > > > > > timeout we're able to block any later completion of the unplug (as we > > > > > can on papr). > > > > > > Is canceling unplug on timeout documented somewhere (like some spec)? > > > > Uh.. not as such. In the PAPR model, hotplugs and unplugs are mostly > > guest directed, so the question doesn't really arise. > > > > > If not it might (theoretically) confuse guest when it tries to unplug > > > after timeout and leave guest in some unexpected state. > > > > Possible, but probably not that likely. The mechanism we use to > > "cancel" the hotplugs is that we just fail the hypercalls that the > > guest will need to call to actually complete the hotplug. We also > > fail those in some other situations, and that seems to work. > > > > That said, I no longer think this cancelling on timeout is a good > > idea, since it mismatches what happens on other platforms more than I > > think we need to. > > > > My now preferred approach is to revert the timeout changes, but > > instead allow retries of unplugs to be issued. I think that's just a > > matter of resending the unplug message to the guest, while making it > > otherwise a no-op on the qemu side. > > I used this approach in a patch I sent back in January: Yes, you did. I rejected it at the time, but the discussion since has convinced me that I made a mistake. In particular, the point that a really loaded host could pretty much arbitrarily extend the time for the guest to process the request is convincing to me. > "[PATCH v2 1/1] spapr.c: always pulse guest IRQ in spapr_core_unplug_request()" Although.. I think we should actually do a full resend of the unplug request message to the queue, not just pulse the irq. AFAICT an unplug request on a DRC that is already unplugged should be safe (remove-LMB-by-count-only requests might have to be an exception). > https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04399.html > > > Let me know and I'll revert the timeout mechanism and re-post this one. > I guess there's still time to make this change in the 6.0.0 window, avoiding > releasing a mechanism we're not happy with. Yes, please, I think this is the way to go. 1) Revert timeouts (6.0) 2) Allow retries (6.0) 3) Add notifications when the guest positively signals failure (6.1) I think this gives us the best mix of a) user experience, b) not allowing nasty edge cases on loaded systems, c) matching x86 behaviour where possible.
Hello, Quick update about this work: - the hotunplug timeout was reverted in the pSeries machine for 6.0.0. This means that we have no use for a DEVICE_NOT_DELETED event or similar. I'll drop it for the next version of the series. - there is a good chance that the pSeries kernel will introduce a way to report hotunplug errors in v5.13 ([1] for more info). This would make the DEVICE_UNPLUG_ERROR event relevant again (otherwise it would just be a rebranding of the existing mem_unplug_error) since we'll be able to properly report guest side unplug errors for all devices in the pSeries machine, starting with CPUs. Thanks, DHB [1] https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210416210216.380291-3-danielhb413@gmail.com/ On 3/12/21 5:07 PM, Daniel Henrique Barboza wrote: > Hi, > > This series adds 2 new QAPI events, DEVICE_NOT_DELETED and > DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. > > Patches 1 and 3 are independent of the ppc patches and can be applied > separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and > are dependent on the QAPI patches. > > > [1] https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg01900.html > > Daniel Henrique Barboza (4): > qapi/qdev.json: add DEVICE_NOT_DELETED event > spapr_drc.c: send DEVICE_NOT_DELETED event on unplug timeout > qapi/machine.json: add DEVICE_UNPLUG_ERROR QAPI event > spapr.c: use DEVICE_UNPLUG_ERROR event in > spapr_memory_unplug_rollback() > > hw/ppc/spapr.c | 2 +- > hw/ppc/spapr_drc.c | 8 ++++++++ > qapi/machine.json | 23 +++++++++++++++++++++++ > qapi/qdev.json | 28 ++++++++++++++++++++++++++++ > 4 files changed, 60 insertions(+), 1 deletion(-) >
Hi, This series adds 2 new QAPI events, DEVICE_NOT_DELETED and DEVICE_UNPLUG_ERROR. They were (and are still being) discussed in [1]. Patches 1 and 3 are independent of the ppc patches and can be applied separately. Patches 2 and 4 are based on David's ppc-for-6.0 branch and are dependent on the QAPI patches. [1] https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg01900.html Daniel Henrique Barboza (4): qapi/qdev.json: add DEVICE_NOT_DELETED event spapr_drc.c: send DEVICE_NOT_DELETED event on unplug timeout qapi/machine.json: add DEVICE_UNPLUG_ERROR QAPI event spapr.c: use DEVICE_UNPLUG_ERROR event in spapr_memory_unplug_rollback() hw/ppc/spapr.c | 2 +- hw/ppc/spapr_drc.c | 8 ++++++++ qapi/machine.json | 23 +++++++++++++++++++++++ qapi/qdev.json | 28 ++++++++++++++++++++++++++++ 4 files changed, 60 insertions(+), 1 deletion(-)