Hey Marc,
On Wed, Aug 18, 2021 at 12:05 PM Raghavendra Rao Ananta
<rananta@xxxxxxxxxx> wrote:
>
> On Wed, Aug 18, 2021 at 11:14 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> >
> > When a mapped level interrupt (a timer, for example) is deactivated
> > by the guest, the corresponding host interrupt is equally deactivated.
> > However, the fate of the pending state still needs to be dealt
> > with in SW.
> >
> > This is specially true when the interrupt was in the active+pending
> > state in the virtual distributor at the point where the guest
> > was entered. On exit, the pending state is potentially stale
> > (the guest may have put the interrupt in a non-pending state).
> >
> > If we don't do anything, the interrupt will be spuriously injected
> > in the guest. Although this shouldn't have any ill effect (spurious
> > interrupts are always possible), we can improve the emulation by
> > detecting the deactivation-while-pending case and resample the
> > interrupt.
> >
> > Fixes: e40cc57bac79 ("KVM: arm/arm64: vgic: Support level-triggered mapped interrupts")
> > Reported-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> > arch/arm64/kvm/vgic/vgic-v2.c | 25 ++++++++++++++++++-------
> > arch/arm64/kvm/vgic/vgic-v3.c | 25 ++++++++++++++++++-------
> > 2 files changed, 36 insertions(+), 14 deletions(-)
> >
> Tested-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
>
> Thanks,
> Raghavendra
> > diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
> > index 2c580204f1dc..3e52ea86a87f 100644
> > --- a/arch/arm64/kvm/vgic/vgic-v2.c
> > +++ b/arch/arm64/kvm/vgic/vgic-v2.c
> > @@ -60,6 +60,7 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
> > u32 val = cpuif->vgic_lr[lr];
> > u32 cpuid, intid = val & GICH_LR_VIRTUALID;
> > struct vgic_irq *irq;
> > + bool deactivated;
> >
> > /* Extract the source vCPU id from the LR */
> > cpuid = val & GICH_LR_PHYSID_CPUID;
> > @@ -75,7 +76,8 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
> >
> > raw_spin_lock(&irq->irq_lock);
> >
> > - /* Always preserve the active bit */
> > + /* Always preserve the active bit, note deactivation */
> > + deactivated = irq->active && !(val & GICH_LR_ACTIVE_BIT);
> > irq->active = !!(val & GICH_LR_ACTIVE_BIT);
> >
> > if (irq->active && vgic_irq_is_sgi(intid))
> > @@ -105,6 +107,12 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
> > * device state could have changed or we simply need to
> > * process the still pending interrupt later.
> > *
> > + * We could also have entered the guest with the interrupt
> > + * active+pending. On the next exit, we need to re-evaluate
> > + * the pending state, as it could otherwise result in a
> > + * spurious interrupt by injecting a now potentially stale
> > + * pending state.
> > + *
> > * If this causes us to lower the level, we have to also clear
> > * the physical active state, since we will otherwise never be
> > * told when the interrupt becomes asserted again.
> > @@ -115,12 +123,15 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
> > if (vgic_irq_is_mapped_level(irq)) {
> > bool resample = false;
> >
> > - if (val & GICH_LR_PENDING_BIT) {
> > - irq->line_level = vgic_get_phys_line_level(irq);
> > - resample = !irq->line_level;
> > - } else if (vgic_irq_needs_resampling(irq) &&
> > - !(irq->active || irq->pending_latch)) {
> > - resample = true;
> > + if (unlikely(vgic_irq_needs_resampling(irq))) {
> > + if (!(irq->active || irq->pending_latch))
> > + resample = true;
> > + } else {
> > + if ((val & GICH_LR_PENDING_BIT) ||
> > + (deactivated && irq->line_level)) {
> > + irq->line_level = vgic_get_phys_line_level(irq);
> > + resample = !irq->line_level;
> > + }
> > }
> >
> > if (resample)
> > diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
> > index 66004f61cd83..74f9aefffd5e 100644
> > --- a/arch/arm64/kvm/vgic/vgic-v3.c
> > +++ b/arch/arm64/kvm/vgic/vgic-v3.c
> > @@ -46,6 +46,7 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
> > u32 intid, cpuid;
> > struct vgic_irq *irq;
> > bool is_v2_sgi = false;
> > + bool deactivated;
> >
> > cpuid = val & GICH_LR_PHYSID_CPUID;
> > cpuid >>= GICH_LR_PHYSID_CPUID_SHIFT;
> > @@ -68,7 +69,8 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
> >
> > raw_spin_lock(&irq->irq_lock);
> >
> > - /* Always preserve the active bit */
> > + /* Always preserve the active bit, note deactivation */
> > + deactivated = irq->active && !(val & ICH_LR_ACTIVE_BIT);
> > irq->active = !!(val & ICH_LR_ACTIVE_BIT);
> >
> > if (irq->active && is_v2_sgi)
> > @@ -98,6 +100,12 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
> > * device state could have changed or we simply need to
> > * process the still pending interrupt later.
> > *
> > + * We could also have entered the guest with the interrupt
> > + * active+pending. On the next exit, we need to re-evaluate
> > + * the pending state, as it could otherwise result in a
> > + * spurious interrupt by injecting a now potentially stale
> > + * pending state.
> > + *
> > * If this causes us to lower the level, we have to also clear
> > * the physical active state, since we will otherwise never be
> > * told when the interrupt becomes asserted again.
> > @@ -108,12 +116,15 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
> > if (vgic_irq_is_mapped_level(irq)) {
> > bool resample = false;
> >
> > - if (val & ICH_LR_PENDING_BIT) {
> > - irq->line_level = vgic_get_phys_line_level(irq);
> > - resample = !irq->line_level;
> > - } else if (vgic_irq_needs_resampling(irq) &&
> > - !(irq->active || irq->pending_latch)) {
> > - resample = true;
> > + if (unlikely(vgic_irq_needs_resampling(irq))) {
> > + if (!(irq->active || irq->pending_latch))
> > + resample = true;
> > + } else {
> > + if ((val & ICH_LR_PENDING_BIT) ||
> > + (deactivated && irq->line_level)) {
> > + irq->line_level = vgic_get_phys_line_level(irq);
> > + resample = !irq->line_level;
> > + }
The vGICv3 and vGICv2 implementations look identical here, should we
have a helper that keeps the code common between the two?
Otherwise, the functional change LGTM, so:
Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>
> > }
> >
> > if (resample)
> > --
> > 2.30.2
> >
