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;
> + }
> }
>
> if (resample)
> --
> 2.30.2
>
