| Message ID | 20200320190737.42110-3-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/nvmx: attempt to fix interrupt injection | expand |
> From: Roger Pau Monne <roger.pau@citrix.com> > Sent: Saturday, March 21, 2020 3:08 AM > > The current usage of nvmx_update_apicv is not clear: it is deeply > intertwined with the Ack interrupt on exit VMEXIT control. > > The code in nvmx_update_apicv should update the SVI (in service interrupt) > field of the guest interrupt status only when the Ack interrupt on > exit is set, as it is used to record that the interrupt being > serviced is signaled in a vmcs field, and hence hasn't been injected > as on native. It's important to record the current in service > interrupt on the guest interrupt status field, or else further > interrupts won't respect the priority of the in service one. > > While clarifying the usage make sure that the SVI is only updated when > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > else a guest not using the Ack on exit feature would loose interrupts as > they would be signaled as being in service on the guest interrupt > status field but won't actually be recorded on the interrupt info vmcs > field, neither injected in any other way. It is insufficient. You also need to update RVI to enable virtual injection when Ack on exit is cleared. > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > --- > xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c > index 1b8461ba30..180d01e385 100644 > --- a/xen/arch/x86/hvm/vmx/vvmx.c > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > @@ -1383,7 +1383,7 @@ static void nvmx_update_apicv(struct vcpu *v) > { > struct nestedvmx *nvmx = &vcpu_2_nvmx(v); > unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); > - uint32_t intr_info = nvmx->intr.intr_info; > + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); well, above reminds me an interesting question. Combining last and this patch, we'd see essentially that it goes back to the state before f96e1469 (at least when Ack on exit is true). iirc, that commit was introduced to enable nested x2apic with apicv, and your very first version even just removed the whole nvmx_update_apicv. Then now with the new reverted logic, are you still suffering x2apic problem? If not, does it imply the real fix is actually coming from patch 3/3 for eoi bitmap update? > > if ( reason == EXIT_REASON_EXTERNAL_INTERRUPT && > nvmx->intr.source == hvm_intsrc_lapic && > @@ -1399,6 +1399,15 @@ static void nvmx_update_apicv(struct vcpu *v) > ppr = vlapic_set_ppr(vlapic); > WARN_ON((ppr & 0xf0) != (vector & 0xf0)); > > + /* > + * SVI must be updated when the interrupt has been signaled using the > + * Ack on exit feature, or else the currently in-service interrupt > + * won't be respected. > + * > + * Note that this is specific to the fact that when doing a VMEXIT an > + * interrupt might get delivered using the interrupt info vmcs field > + * instead of being injected normally. > + */ I'm not sure mentioning SVI specifically here is necessary, since all steps here are required - updating iir, isr, rvi, svi, ppr, etc. It is just an emulation of updating virtual APIC state as if a virtual interrupt delivery happens. > status = vector << VMX_GUEST_INTR_STATUS_SVI_OFFSET; > rvi = vlapic_has_pending_irq(v); > if ( rvi != -1 ) > -- > 2.25.0
On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > From: Roger Pau Monne <roger.pau@citrix.com> > > Sent: Saturday, March 21, 2020 3:08 AM > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > The code in nvmx_update_apicv should update the SVI (in service interrupt) > > field of the guest interrupt status only when the Ack interrupt on > > exit is set, as it is used to record that the interrupt being > > serviced is signaled in a vmcs field, and hence hasn't been injected > > as on native. It's important to record the current in service > > interrupt on the guest interrupt status field, or else further > > interrupts won't respect the priority of the in service one. > > > > While clarifying the usage make sure that the SVI is only updated when > > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > > else a guest not using the Ack on exit feature would loose interrupts as > > they would be signaled as being in service on the guest interrupt > > status field but won't actually be recorded on the interrupt info vmcs > > field, neither injected in any other way. > > It is insufficient. You also need to update RVI to enable virtual injection > when Ack on exit is cleared. But RVI should be updated in vmx_intr_assist in that case, since nvmx_intr_intercept shouldn't intercept the interrupt, as it should be handled normally. > > > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > > --- > > xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c > > index 1b8461ba30..180d01e385 100644 > > --- a/xen/arch/x86/hvm/vmx/vvmx.c > > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > > @@ -1383,7 +1383,7 @@ static void (struct vcpu *v) > > { > > struct nestedvmx *nvmx = &vcpu_2_nvmx(v); > > unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); > > - uint32_t intr_info = nvmx->intr.intr_info; > > + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); > > well, above reminds me an interesting question. Combining last and this > patch, we'd see essentially that it goes back to the state before f96e1469 > (at least when Ack on exit is true). Well, patch 1/3 is a revert of f96e1469, so just reverting f96e1469 gets us to that state. This patch is an attempt to clarify that nvmx_update_apicv is closely related to the Ack on exit feature, as it modifies SVI in order to signal the vector currently being serviced by the EXIT_INTR_INFO vmcs field. This was not obvious to me, as at first sight I assumed nvmx_update_apicv was actually injecting that vector into the guest. > iirc, that commit was introduced to enable > nested x2apic with apicv, and your very first version even just removed > the whole nvmx_update_apicv. Then now with the new reverted logic, > are you still suffering x2apic problem? If not, does it imply the real fix > is actually coming from patch 3/3 for eoi bitmap update? Yes, patch 3/3 is the one that fixed the issue. Note however that strangely enough removing the call to nvmx_update_apicv (as my first attempt to solve the issue) did fix it on one of my boxes. It depends a lot on the available vmx features AFAICT. > > > > if ( reason == EXIT_REASON_EXTERNAL_INTERRUPT && > > nvmx->intr.source == hvm_intsrc_lapic && > > @@ -1399,6 +1399,15 @@ static void nvmx_update_apicv(struct vcpu *v) > > ppr = vlapic_set_ppr(vlapic); > > WARN_ON((ppr & 0xf0) != (vector & 0xf0)); > > > > + /* > > + * SVI must be updated when the interrupt has been signaled using the > > + * Ack on exit feature, or else the currently in-service interrupt > > + * won't be respected. > > + * > > + * Note that this is specific to the fact that when doing a VMEXIT an > > + * interrupt might get delivered using the interrupt info vmcs field > > + * instead of being injected normally. > > + */ > > I'm not sure mentioning SVI specifically here is necessary, since all steps > here are required - updating iir, isr, rvi, svi, ppr, etc. It is just an emulation > of updating virtual APIC state as if a virtual interrupt delivery happens. Hm, it was hard for me to figure out that SVI is modified here in order to signal that the Ack on exit vector is currently in service, as opposed to being injected using the virtual interrupt delivery mechanism. I just wanted to clarify that the purpose of this function is not to inject the vector in intr_info, but rather to signal that such vector has already been injected using a different mechanism. I'm happy to reword this, but IMO it should be clear that the purpose of the function is not so much to inject an interrupt, but to update the virtual interrupt delivery field in order to signal that an interrupt has been injected using a different mechanism. Thanks, Roger.
> From: Roger Pau Monné <roger.pau@citrix.com> > Sent: Tuesday, March 24, 2020 5:51 PM > > On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > > From: Roger Pau Monne <roger.pau@citrix.com> > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > > > The code in nvmx_update_apicv should update the SVI (in service > interrupt) > > > field of the guest interrupt status only when the Ack interrupt on > > > exit is set, as it is used to record that the interrupt being > > > serviced is signaled in a vmcs field, and hence hasn't been injected > > > as on native. It's important to record the current in service > > > interrupt on the guest interrupt status field, or else further > > > interrupts won't respect the priority of the in service one. > > > > > > While clarifying the usage make sure that the SVI is only updated when > > > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > > > else a guest not using the Ack on exit feature would loose interrupts as > > > they would be signaled as being in service on the guest interrupt > > > status field but won't actually be recorded on the interrupt info vmcs > > > field, neither injected in any other way. > > > > It is insufficient. You also need to update RVI to enable virtual injection > > when Ack on exit is cleared. > > But RVI should be updated in vmx_intr_assist in that case, since > nvmx_intr_intercept shouldn't intercept the interrupt, as it should be > handled normally. As we discussed before, vmx_intr_assist is invoked before nvmx_switch_guest. It is incorrectly to update RVI at that time since it might be still vmcs02 being active (if no pending softirq to make it invoked again). Also nvmx_intr_intercept does intercept Ack-on-exit=0 case: if ( intack.source == hvm_intsrc_pic || intack.source == hvm_intsrc_lapic ) { vmx_inject_extint(intack.vector, intack.source); ctrl = get_vvmcs(v, VM_EXIT_CONTROLS); if ( ctrl & VM_EXIT_ACK_INTR_ON_EXIT ) { /* for now, duplicate the ack path in vmx_intr_assist */ hvm_vcpu_ack_pending_irq(v, intack); pt_intr_post(v, intack); intack = hvm_vcpu_has_pending_irq(v); if ( unlikely(intack.source != hvm_intsrc_none) ) vmx_enable_intr_window(v, intack); } else if ( !cpu_has_vmx_virtual_intr_delivery ) vmx_enable_intr_window(v, intack); return 1; <<<<<<<< } > > > > > > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > > > --- > > > xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- > > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > > > diff --git a/xen/arch/x86/hvm/vmx/vvmx.c > b/xen/arch/x86/hvm/vmx/vvmx.c > > > index 1b8461ba30..180d01e385 100644 > > > --- a/xen/arch/x86/hvm/vmx/vvmx.c > > > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > > > @@ -1383,7 +1383,7 @@ static void (struct vcpu *v) > > > { > > > struct nestedvmx *nvmx = &vcpu_2_nvmx(v); > > > unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); > > > - uint32_t intr_info = nvmx->intr.intr_info; > > > + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); > > > > well, above reminds me an interesting question. Combining last and this > > patch, we'd see essentially that it goes back to the state before f96e1469 > > (at least when Ack on exit is true). > > Well, patch 1/3 is a revert of f96e1469, so just reverting f96e1469 > gets us to that state. you are right. I just wanted to point out that this patch alone doesn't do any real fix for ack-on-exit=1 case. It just makes sure that ack-on-exit=0 is skipped from that function. So it won't be the one fixing your previous problem.
On Tue, Mar 24, 2020 at 10:11:15AM +0000, Tian, Kevin wrote: > > From: Roger Pau Monné <roger.pau@citrix.com> > > Sent: Tuesday, March 24, 2020 5:51 PM > > > > On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > > > From: Roger Pau Monne <roger.pau@citrix.com> > > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > > > > > The code in nvmx_update_apicv should update the SVI (in service > > interrupt) > > > > field of the guest interrupt status only when the Ack interrupt on > > > > exit is set, as it is used to record that the interrupt being > > > > serviced is signaled in a vmcs field, and hence hasn't been injected > > > > as on native. It's important to record the current in service > > > > interrupt on the guest interrupt status field, or else further > > > > interrupts won't respect the priority of the in service one. > > > > > > > > While clarifying the usage make sure that the SVI is only updated when > > > > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > > > > else a guest not using the Ack on exit feature would loose interrupts as > > > > they would be signaled as being in service on the guest interrupt > > > > status field but won't actually be recorded on the interrupt info vmcs > > > > field, neither injected in any other way. > > > > > > It is insufficient. You also need to update RVI to enable virtual injection > > > when Ack on exit is cleared. > > > > But RVI should be updated in vmx_intr_assist in that case, since > > nvmx_intr_intercept shouldn't intercept the interrupt, as it should be > > handled normally. > > As we discussed before, vmx_intr_assist is invoked before nvmx_switch_guest. > > It is incorrectly to update RVI at that time since it might be still vmcs02 being > active (if no pending softirq to make it invoked again). > > Also nvmx_intr_intercept does intercept Ack-on-exit=0 case: > > if ( intack.source == hvm_intsrc_pic || > intack.source == hvm_intsrc_lapic ) > { > vmx_inject_extint(intack.vector, intack.source); > > ctrl = get_vvmcs(v, VM_EXIT_CONTROLS); > if ( ctrl & VM_EXIT_ACK_INTR_ON_EXIT ) > { > /* for now, duplicate the ack path in vmx_intr_assist */ > hvm_vcpu_ack_pending_irq(v, intack); > pt_intr_post(v, intack); > > intack = hvm_vcpu_has_pending_irq(v); > if ( unlikely(intack.source != hvm_intsrc_none) ) > vmx_enable_intr_window(v, intack); > } > else if ( !cpu_has_vmx_virtual_intr_delivery ) > vmx_enable_intr_window(v, intack); > > return 1; <<<<<<<< Right, I always get confused by the switch happening in the vmentry path. That only happens when the vcpu is in nested mode (nestedhvm_vcpu_in_guestmode == true). That would be the case before a vmexit, at least for the first call to vmx_intr_assist if there are pending softirqs. Note that if there are pending softirqs the second time nvmx_intr_intercept will return 0. > } > > > > > > > > > > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > > > > --- > > > > xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- > > > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/xen/arch/x86/hvm/vmx/vvmx.c > > b/xen/arch/x86/hvm/vmx/vvmx.c > > > > index 1b8461ba30..180d01e385 100644 > > > > --- a/xen/arch/x86/hvm/vmx/vvmx.c > > > > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > > > > @@ -1383,7 +1383,7 @@ static void (struct vcpu *v) > > > > { > > > > struct nestedvmx *nvmx = &vcpu_2_nvmx(v); > > > > unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); > > > > - uint32_t intr_info = nvmx->intr.intr_info; > > > > + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); > > > > > > well, above reminds me an interesting question. Combining last and this > > > patch, we'd see essentially that it goes back to the state before f96e1469 > > > (at least when Ack on exit is true). > > > > Well, patch 1/3 is a revert of f96e1469, so just reverting f96e1469 > > gets us to that state. > > you are right. I just wanted to point out that this patch alone doesn't > do any real fix for ack-on-exit=1 case. It just makes sure that ack-on-exit=0 > is skipped from that function. So it won't be the one fixing your previous > problem.
> From: Roger Pau Monné <roger.pau@citrix.com> > Sent: Tuesday, March 24, 2020 7:23 PM > > On Tue, Mar 24, 2020 at 10:11:15AM +0000, Tian, Kevin wrote: > > > From: Roger Pau Monné <roger.pau@citrix.com> > > > Sent: Tuesday, March 24, 2020 5:51 PM > > > > > > On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > > > > From: Roger Pau Monne <roger.pau@citrix.com> > > > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > > > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > > > > > > > The code in nvmx_update_apicv should update the SVI (in service > > > interrupt) > > > > > field of the guest interrupt status only when the Ack interrupt on > > > > > exit is set, as it is used to record that the interrupt being > > > > > serviced is signaled in a vmcs field, and hence hasn't been injected > > > > > as on native. It's important to record the current in service > > > > > interrupt on the guest interrupt status field, or else further > > > > > interrupts won't respect the priority of the in service one. > > > > > > > > > > While clarifying the usage make sure that the SVI is only updated > when > > > > > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > > > > > else a guest not using the Ack on exit feature would loose interrupts > as > > > > > they would be signaled as being in service on the guest interrupt > > > > > status field but won't actually be recorded on the interrupt info vmcs > > > > > field, neither injected in any other way. > > > > > > > > It is insufficient. You also need to update RVI to enable virtual injection > > > > when Ack on exit is cleared. > > > > > > But RVI should be updated in vmx_intr_assist in that case, since > > > nvmx_intr_intercept shouldn't intercept the interrupt, as it should be > > > handled normally. > > > > As we discussed before, vmx_intr_assist is invoked before > nvmx_switch_guest. > > > > It is incorrectly to update RVI at that time since it might be still vmcs02 > being > > active (if no pending softirq to make it invoked again). > > > > Also nvmx_intr_intercept does intercept Ack-on-exit=0 case: > > > > if ( intack.source == hvm_intsrc_pic || > > intack.source == hvm_intsrc_lapic ) > > { > > vmx_inject_extint(intack.vector, intack.source); > > > > ctrl = get_vvmcs(v, VM_EXIT_CONTROLS); > > if ( ctrl & VM_EXIT_ACK_INTR_ON_EXIT ) > > { > > /* for now, duplicate the ack path in vmx_intr_assist */ > > hvm_vcpu_ack_pending_irq(v, intack); > > pt_intr_post(v, intack); > > > > intack = hvm_vcpu_has_pending_irq(v); > > if ( unlikely(intack.source != hvm_intsrc_none) ) > > vmx_enable_intr_window(v, intack); > > } > > else if ( !cpu_has_vmx_virtual_intr_delivery ) > > vmx_enable_intr_window(v, intack); > > > > return 1; <<<<<<<< > > Right, I always get confused by the switch happening in the vmentry > path. > > That only happens when the vcpu is in nested mode > (nestedhvm_vcpu_in_guestmode == true). That would be the case before a > vmexit, at least for the first call to vmx_intr_assist if there are > pending softirqs. > > Note that if there are pending softirqs the second time > nvmx_intr_intercept will return 0. Exactly. > > > } > > > > > > > > > > > > > > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > > > > > --- > > > > > xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- > > > > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/xen/arch/x86/hvm/vmx/vvmx.c > > > b/xen/arch/x86/hvm/vmx/vvmx.c > > > > > index 1b8461ba30..180d01e385 100644 > > > > > --- a/xen/arch/x86/hvm/vmx/vvmx.c > > > > > +++ b/xen/arch/x86/hvm/vmx/vvmx.c > > > > > @@ -1383,7 +1383,7 @@ static void (struct vcpu *v) > > > > > { > > > > > struct nestedvmx *nvmx = &vcpu_2_nvmx(v); > > > > > unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); > > > > > - uint32_t intr_info = nvmx->intr.intr_info; > > > > > + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); > > > > > > > > well, above reminds me an interesting question. Combining last and this > > > > patch, we'd see essentially that it goes back to the state before > f96e1469 > > > > (at least when Ack on exit is true). > > > > > > Well, patch 1/3 is a revert of f96e1469, so just reverting f96e1469 > > > gets us to that state. > > > > you are right. I just wanted to point out that this patch alone doesn't > > do any real fix for ack-on-exit=1 case. It just makes sure that ack-on-exit=0 > > is skipped from that function. So it won't be the one fixing your previous > > problem.
On Tue, Mar 24, 2020 at 11:33:00AM +0000, Tian, Kevin wrote: > > From: Roger Pau Monné <roger.pau@citrix.com> > > Sent: Tuesday, March 24, 2020 7:23 PM > > > > On Tue, Mar 24, 2020 at 10:11:15AM +0000, Tian, Kevin wrote: > > > > From: Roger Pau Monné <roger.pau@citrix.com> > > > > Sent: Tuesday, March 24, 2020 5:51 PM > > > > > > > > On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > > > > > From: Roger Pau Monne <roger.pau@citrix.com> > > > > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > > > > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > > > > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > > > > > > > > > The code in nvmx_update_apicv should update the SVI (in service > > > > interrupt) > > > > > > field of the guest interrupt status only when the Ack interrupt on > > > > > > exit is set, as it is used to record that the interrupt being > > > > > > serviced is signaled in a vmcs field, and hence hasn't been injected > > > > > > as on native. It's important to record the current in service > > > > > > interrupt on the guest interrupt status field, or else further > > > > > > interrupts won't respect the priority of the in service one. > > > > > > > > > > > > While clarifying the usage make sure that the SVI is only updated > > when > > > > > > Ack on exit is set and the nested vmcs interrupt info field is valid. Or > > > > > > else a guest not using the Ack on exit feature would loose interrupts > > as > > > > > > they would be signaled as being in service on the guest interrupt > > > > > > status field but won't actually be recorded on the interrupt info vmcs > > > > > > field, neither injected in any other way. > > > > > > > > > > It is insufficient. You also need to update RVI to enable virtual injection > > > > > when Ack on exit is cleared. > > > > > > > > But RVI should be updated in vmx_intr_assist in that case, since > > > > nvmx_intr_intercept shouldn't intercept the interrupt, as it should be > > > > handled normally. > > > > > > As we discussed before, vmx_intr_assist is invoked before > > nvmx_switch_guest. > > > > > > It is incorrectly to update RVI at that time since it might be still vmcs02 > > being > > > active (if no pending softirq to make it invoked again). > > > > > > Also nvmx_intr_intercept does intercept Ack-on-exit=0 case: > > > > > > if ( intack.source == hvm_intsrc_pic || > > > intack.source == hvm_intsrc_lapic ) I've realized that nvmx_intr_intercept will return 1 for interrupts originating from the lapic or the pic, while nvmx_update_apicv will only update GUEST_INTR_STATUS for interrupts originating from the lapic. Is this correct? Shouldn't both be in sync and handle the same interrupt sources? Thanks, Roger.
> From: Roger Pau Monné <roger.pau@citrix.com> > Sent: Tuesday, March 24, 2020 8:19 PM > > On Tue, Mar 24, 2020 at 11:33:00AM +0000, Tian, Kevin wrote: > > > From: Roger Pau Monné <roger.pau@citrix.com> > > > Sent: Tuesday, March 24, 2020 7:23 PM > > > > > > On Tue, Mar 24, 2020 at 10:11:15AM +0000, Tian, Kevin wrote: > > > > > From: Roger Pau Monné <roger.pau@citrix.com> > > > > > Sent: Tuesday, March 24, 2020 5:51 PM > > > > > > > > > > On Tue, Mar 24, 2020 at 06:03:28AM +0000, Tian, Kevin wrote: > > > > > > > From: Roger Pau Monne <roger.pau@citrix.com> > > > > > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > > > > > > > > > The current usage of nvmx_update_apicv is not clear: it is deeply > > > > > > > intertwined with the Ack interrupt on exit VMEXIT control. > > > > > > > > > > > > > > The code in nvmx_update_apicv should update the SVI (in service > > > > > interrupt) > > > > > > > field of the guest interrupt status only when the Ack interrupt on > > > > > > > exit is set, as it is used to record that the interrupt being > > > > > > > serviced is signaled in a vmcs field, and hence hasn't been injected > > > > > > > as on native. It's important to record the current in service > > > > > > > interrupt on the guest interrupt status field, or else further > > > > > > > interrupts won't respect the priority of the in service one. > > > > > > > > > > > > > > While clarifying the usage make sure that the SVI is only updated > > > when > > > > > > > Ack on exit is set and the nested vmcs interrupt info field is valid. > Or > > > > > > > else a guest not using the Ack on exit feature would loose > interrupts > > > as > > > > > > > they would be signaled as being in service on the guest interrupt > > > > > > > status field but won't actually be recorded on the interrupt info > vmcs > > > > > > > field, neither injected in any other way. > > > > > > > > > > > > It is insufficient. You also need to update RVI to enable virtual > injection > > > > > > when Ack on exit is cleared. > > > > > > > > > > But RVI should be updated in vmx_intr_assist in that case, since > > > > > nvmx_intr_intercept shouldn't intercept the interrupt, as it should be > > > > > handled normally. > > > > > > > > As we discussed before, vmx_intr_assist is invoked before > > > nvmx_switch_guest. > > > > > > > > It is incorrectly to update RVI at that time since it might be still vmcs02 > > > being > > > > active (if no pending softirq to make it invoked again). > > > > > > > > Also nvmx_intr_intercept does intercept Ack-on-exit=0 case: > > > > > > > > if ( intack.source == hvm_intsrc_pic || > > > > intack.source == hvm_intsrc_lapic ) > > I've realized that nvmx_intr_intercept will return 1 for interrupts > originating from the lapic or the pic, while nvmx_update_apicv will > only update GUEST_INTR_STATUS for interrupts originating from the > lapic. Is this correct? Isn't apicv for virtual lapic instead of virtual pic? > > Shouldn't both be in sync and handle the same interrupt sources? > But I do realize one potential issue about 67f9d0b9, which may break vpic delivery when ack-on-exit is off. We should always use interrupt window to handle that situation for vpic. Sorry I didn't catch it when proposing that change... Thanks Kevin
diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c index 1b8461ba30..180d01e385 100644 --- a/xen/arch/x86/hvm/vmx/vvmx.c +++ b/xen/arch/x86/hvm/vmx/vvmx.c @@ -1383,7 +1383,7 @@ static void nvmx_update_apicv(struct vcpu *v) { struct nestedvmx *nvmx = &vcpu_2_nvmx(v); unsigned long reason = get_vvmcs(v, VM_EXIT_REASON); - uint32_t intr_info = nvmx->intr.intr_info; + unsigned long intr_info = get_vvmcs(v, VM_EXIT_INTR_INFO); if ( reason == EXIT_REASON_EXTERNAL_INTERRUPT && nvmx->intr.source == hvm_intsrc_lapic && @@ -1399,6 +1399,15 @@ static void nvmx_update_apicv(struct vcpu *v) ppr = vlapic_set_ppr(vlapic); WARN_ON((ppr & 0xf0) != (vector & 0xf0)); + /* + * SVI must be updated when the interrupt has been signaled using the + * Ack on exit feature, or else the currently in-service interrupt + * won't be respected. + * + * Note that this is specific to the fact that when doing a VMEXIT an + * interrupt might get delivered using the interrupt info vmcs field + * instead of being injected normally. + */ status = vector << VMX_GUEST_INTR_STATUS_SVI_OFFSET; rvi = vlapic_has_pending_irq(v); if ( rvi != -1 )
The current usage of nvmx_update_apicv is not clear: it is deeply intertwined with the Ack interrupt on exit VMEXIT control. The code in nvmx_update_apicv should update the SVI (in service interrupt) field of the guest interrupt status only when the Ack interrupt on exit is set, as it is used to record that the interrupt being serviced is signaled in a vmcs field, and hence hasn't been injected as on native. It's important to record the current in service interrupt on the guest interrupt status field, or else further interrupts won't respect the priority of the in service one. While clarifying the usage make sure that the SVI is only updated when Ack on exit is set and the nested vmcs interrupt info field is valid. Or else a guest not using the Ack on exit feature would loose interrupts as they would be signaled as being in service on the guest interrupt status field but won't actually be recorded on the interrupt info vmcs field, neither injected in any other way. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- xen/arch/x86/hvm/vmx/vvmx.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)