| Message ID | 20190816023528.30210-3-tina.zhang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Deliver vGPU display refresh event to userspace | expand |
On Fri, 16 Aug 2019 10:35:24 +0800 Tina Zhang <tina.zhang@intel.com> wrote: > Introduce vGPU specific irq type VFIO_IRQ_TYPE_GFX, and > VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ as the subtype for vGPU display. > > Introduce vfio_irq_info_cap_display_plane_events capability to notify > user space with the vGPU's plane update events > > v2: > - Add VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ description. (Alex & Kechen) > - Introduce vfio_irq_info_cap_display_plane_events. (Gerd & Alex) > > Signed-off-by: Tina Zhang <tina.zhang@intel.com> > --- > include/uapi/linux/vfio.h | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index d83c9f136a5b..21ac69f0e1a9 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -465,6 +465,27 @@ struct vfio_irq_info_cap_type { > __u32 subtype; /* type specific */ > }; > > +#define VFIO_IRQ_TYPE_GFX (1) > +/* > + * vGPU vendor sub-type > + * vGPU device display related interrupts e.g. vblank/pageflip > + */ > +#define VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ (1) If this is a GFX/DISPLAY IRQ, why are we talking about a "vGPU" in the description? It's not specific to a vGPU implementation, right? Is this related to a physical display or a virtual display? If it's related to the GFX PLANE ioctls, it should state that. It's not well specified what this interrupt signals. Is it vblank? Is it pageflip? Is it both? Neither? Something else? > + > +/* > + * Display capability of using one eventfd to notify user space with the > + * vGPU's plane update events. > + * cur_event_val: eventfd value stands for cursor plane change event. > + * pri_event_val: eventfd value stands for primary plane change event. > + */ > +#define VFIO_IRQ_INFO_CAP_DISPLAY 4 > + > +struct vfio_irq_info_cap_display_plane_events { > + struct vfio_info_cap_header header; > + __u64 cur_event_val; > + __u64 pri_event_val; > +}; Again, what display? Does this reference a GFX plane? The event_val data is not well specified, examples might be necessary. They seem to be used as a flag bit, so should we simply define a bit index for the flag rather than a u64 value? Where are the actual events per plane defined? I'm not sure this patch shouldn't be rolled back into 1, I couldn't find the previous discussion that triggered it to be separate. Perhaps simply for sharing with the work Eric is doing? If so, that's fine, but maybe make note of it in the cover letter. Thanks, Alex
> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@redhat.com] > Sent: Saturday, August 17, 2019 4:52 AM > To: Zhang, Tina <tina.zhang@intel.com> > Cc: intel-gvt-dev@lists.freedesktop.org; kraxel@redhat.com; > kvm@vger.kernel.org; linux-kernel@vger.kernel.org; Yuan, Hang > <hang.yuan@intel.com>; Lv, Zhiyuan <zhiyuan.lv@intel.com> > Subject: Re: [PATCH v5 2/6] vfio: Introduce vGPU display irq type > > On Fri, 16 Aug 2019 10:35:24 +0800 > Tina Zhang <tina.zhang@intel.com> wrote: > > > Introduce vGPU specific irq type VFIO_IRQ_TYPE_GFX, and > > VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ as the subtype for vGPU display. > > > > Introduce vfio_irq_info_cap_display_plane_events capability to notify > > user space with the vGPU's plane update events > > > > v2: > > - Add VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ description. (Alex & Kechen) > > - Introduce vfio_irq_info_cap_display_plane_events. (Gerd & Alex) > > > > Signed-off-by: Tina Zhang <tina.zhang@intel.com> > > --- > > include/uapi/linux/vfio.h | 21 +++++++++++++++++++++ > > 1 file changed, 21 insertions(+) > > > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > > index d83c9f136a5b..21ac69f0e1a9 100644 > > --- a/include/uapi/linux/vfio.h > > +++ b/include/uapi/linux/vfio.h > > @@ -465,6 +465,27 @@ struct vfio_irq_info_cap_type { > > __u32 subtype; /* type specific */ > > }; > > > > +#define VFIO_IRQ_TYPE_GFX (1) > > +/* > > + * vGPU vendor sub-type > > + * vGPU device display related interrupts e.g. vblank/pageflip */ > > +#define VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ (1) > > If this is a GFX/DISPLAY IRQ, why are we talking about a "vGPU" in the > description? It's not specific to a vGPU implementation, right? Is this > related to a physical display or a virtual display? If it's related to the GFX > PLANE ioctls, it should state that. It's not well specified what this interrupt > signals. Is it vblank? Is it pageflip? > Is it both? Neither? Something else? Sorry for the confusion caused here. The original idea here was to use VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ to notify user space with the display refresh event. The display refresh event is general. When notified, user space can use VFIO_DEVICE_QUERY_GFX_PLANE and VFIO_DEVICE_GET_GFX_DMABUF to get the updated framebuffer, instead of polling them all the time. In order to give user space more choice to do the optimization, vfio_irq_info_cap_display_plane_events is proposed to tell user space the different plane refresh event values. So when notified by VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ, user space can get the value of the eventfd counter and understand which plane the event refresh event comes from and choose to get the framebuffer on that plane instead of all the planes. So, from the VFIO user point of view, there is only the display refresh event (i.e. no other events like vblank, pageflip ...). For GTV-g, this display refresh event is implemented by both vblank and pageflip, which is only the implementation thing and can be transparent to the user space. Again sorry about the confusion cased here, I'll correct the comments in the next version. BTW, IIRC, we might also have one question waiting to be replied: - Can we just use VFIO_IRQ_TYPE_GFX w/o proposing a new sub type (i.e. VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ)? Well, only if we can agree on that we don't have any other GFX IRQ requirements in future. Otherwise, we might need a sub type to differentiate them. Thanks. BR, Tina > > > + > > +/* > > + * Display capability of using one eventfd to notify user space with > > +the > > + * vGPU's plane update events. > > + * cur_event_val: eventfd value stands for cursor plane change event. > > + * pri_event_val: eventfd value stands for primary plane change event. > > + */ > > +#define VFIO_IRQ_INFO_CAP_DISPLAY 4 > > + > > +struct vfio_irq_info_cap_display_plane_events { > > + struct vfio_info_cap_header header; > > + __u64 cur_event_val; > > + __u64 pri_event_val; > > +}; > > Again, what display? Does this reference a GFX plane? The event_val data is > not well specified, examples might be necessary. They seem to be used as a > flag bit, so should we simply define a bit index for the flag rather than a u64 > value? Where are the actual events per plane defined? > > I'm not sure this patch shouldn't be rolled back into 1, I couldn't find the > previous discussion that triggered it to be separate. Perhaps simply for > sharing with the work Eric is doing? If so, that's fine, but maybe make note > of it in the cover letter. Thanks, > > Alex
> > > +#define VFIO_IRQ_TYPE_GFX (1) > > > +/* > > > + * vGPU vendor sub-type > > > + * vGPU device display related interrupts e.g. vblank/pageflip */ > > > +#define VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ (1) > > > > If this is a GFX/DISPLAY IRQ, why are we talking about a "vGPU" in the > > description? It's not specific to a vGPU implementation, right? Is this > > related to a physical display or a virtual display? If it's related to the GFX > > PLANE ioctls, it should state that. It's not well specified what this interrupt > > signals. Is it vblank? Is it pageflip? > > Is it both? Neither? Something else? > > Sorry for the confusion caused here. > > The original idea here was to use VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ to > notify user space with the display refresh event. The display refresh > event is general. When notified, user space can use > VFIO_DEVICE_QUERY_GFX_PLANE and VFIO_DEVICE_GET_GFX_DMABUF to get the > updated framebuffer, instead of polling them all the time. > > In order to give user space more choice to do the optimization, > vfio_irq_info_cap_display_plane_events is proposed to tell user space > the different plane refresh event values. So when notified by > VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ, user space can get the value of the > eventfd counter and understand which plane the event refresh event > comes from and choose to get the framebuffer on that plane instead of > all the planes. > > So, from the VFIO user point of view, there is only the display > refresh event (i.e. no other events like vblank, pageflip ...). For > GTV-g, this display refresh event is implemented by both vblank and > pageflip, which is only the implementation thing and can be > transparent to the user space. Again sorry about the confusion cased > here, I'll correct the comments in the next version. All this should be explained in a comment for the IRQ in the header file. Key point for the API is that (a) this is a "the display should be updated" event and (b) this covers all display updates, i.e. user space can stop the display update timer and fully depend on getting notifications if an update is needed. That GTV-g watches guest pageflips is an implementation detail. Should nvidia support this they will probably do something completely different. As far I know they render the guest display to some framebuffer at something like 10fps, so it would make sense for them to send an event each time they refreshed the framebuffer. Also note the relationships (cur_event_val is for DRM_PLANE_TYPE_CURSOR updates and pri_event_val for DRM_PLANE_TYPE_PRIMARY). cheers, Gerd
On Tue, 20 Aug 2019 09:20:30 +0200 "kraxel@redhat.com" <kraxel@redhat.com> wrote: > > > > +#define VFIO_IRQ_TYPE_GFX (1) > > > > +/* > > > > + * vGPU vendor sub-type > > > > + * vGPU device display related interrupts e.g. vblank/pageflip */ > > > > +#define VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ (1) > > > > > > If this is a GFX/DISPLAY IRQ, why are we talking about a "vGPU" in the > > > description? It's not specific to a vGPU implementation, right? Is this > > > related to a physical display or a virtual display? If it's related to the GFX > > > PLANE ioctls, it should state that. It's not well specified what this interrupt > > > signals. Is it vblank? Is it pageflip? > > > Is it both? Neither? Something else? > > > > Sorry for the confusion caused here. > > > > The original idea here was to use VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ to > > notify user space with the display refresh event. The display refresh > > event is general. When notified, user space can use > > VFIO_DEVICE_QUERY_GFX_PLANE and VFIO_DEVICE_GET_GFX_DMABUF to get the > > updated framebuffer, instead of polling them all the time. > > > > In order to give user space more choice to do the optimization, > > vfio_irq_info_cap_display_plane_events is proposed to tell user space > > the different plane refresh event values. So when notified by > > VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ, user space can get the value of the > > eventfd counter and understand which plane the event refresh event > > comes from and choose to get the framebuffer on that plane instead of > > all the planes. > > > > So, from the VFIO user point of view, there is only the display > > refresh event (i.e. no other events like vblank, pageflip ...). For > > GTV-g, this display refresh event is implemented by both vblank and > > pageflip, which is only the implementation thing and can be > > transparent to the user space. Again sorry about the confusion cased > > here, I'll correct the comments in the next version. > > All this should be explained in a comment for the IRQ in the header file. Yes, Tina's update and your clarification all make sense to me, but it needs to be specified in the header how this is supposed to work, what events get signaled and what the user is intended to do in response to that signal. The information is all here, it just needs to be included in the uapi definition. Thanks, Alex > Key point for the API is that (a) this is a "the display should be > updated" event and (b) this covers all display updates, i.e. user space > can stop the display update timer and fully depend on getting > notifications if an update is needed. > > That GTV-g watches guest pageflips is an implementation detail. Should > nvidia support this they will probably do something completely > different. As far I know they render the guest display to some > framebuffer at something like 10fps, so it would make sense for them to > send an event each time they refreshed the framebuffer. > > Also note the relationships (cur_event_val is for DRM_PLANE_TYPE_CURSOR > updates and pri_event_val for DRM_PLANE_TYPE_PRIMARY).
On Tue, 20 Aug 2019 02:12:10 +0000 "Zhang, Tina" <tina.zhang@intel.com> wrote: > BTW, IIRC, we might also have one question waiting to be replied: > - Can we just use VFIO_IRQ_TYPE_GFX w/o proposing a new sub type > (i.e. VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ)? Well, only if we can agree > on that we don't have any other GFX IRQ requirements in future. > Otherwise, we might need a sub type to differentiate them. I think you've answered your own question ;) We already have the infrastructure for defining type/sub-type and it allows us to categorize and group interrupt types together consistent with how we do for regions, so what's the overhead in this approach? Otherwise we tend to have an ad-hoc list. We can't say with absolute certainty that we won't have additional GFX related IRQs. Thanks, Alex
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index d83c9f136a5b..21ac69f0e1a9 100644 --- a/include/uapi/linux/vfio.h +++ b/include/uapi/linux/vfio.h @@ -465,6 +465,27 @@ struct vfio_irq_info_cap_type { __u32 subtype; /* type specific */ }; +#define VFIO_IRQ_TYPE_GFX (1) +/* + * vGPU vendor sub-type + * vGPU device display related interrupts e.g. vblank/pageflip + */ +#define VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ (1) + +/* + * Display capability of using one eventfd to notify user space with the + * vGPU's plane update events. + * cur_event_val: eventfd value stands for cursor plane change event. + * pri_event_val: eventfd value stands for primary plane change event. + */ +#define VFIO_IRQ_INFO_CAP_DISPLAY 4 + +struct vfio_irq_info_cap_display_plane_events { + struct vfio_info_cap_header header; + __u64 cur_event_val; + __u64 pri_event_val; +}; + /** * VFIO_DEVICE_SET_IRQS - _IOW(VFIO_TYPE, VFIO_BASE + 10, struct vfio_irq_set) *
Introduce vGPU specific irq type VFIO_IRQ_TYPE_GFX, and VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ as the subtype for vGPU display. Introduce vfio_irq_info_cap_display_plane_events capability to notify user space with the vGPU's plane update events v2: - Add VFIO_IRQ_SUBTYPE_GFX_DISPLAY_IRQ description. (Alex & Kechen) - Introduce vfio_irq_info_cap_display_plane_events. (Gerd & Alex) Signed-off-by: Tina Zhang <tina.zhang@intel.com> --- include/uapi/linux/vfio.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)