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* [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
@ 2022-02-08 12:37 ` Marc Zyngier
  0 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2022-02-08 12:37 UTC (permalink / raw)
  To: linux-arm-kernel, kvmarm, kvm; +Cc: kernel-team

It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
result in the pending interrupts being accurately reported if they are
mapped to a HW interrupt. This is particularily visible when acking
the timer interrupt and reading the GICR_ISPENDR1 register immediately
after, for example (the interrupt appears as not-pending while it really
is...).

This is because a HW interrupt has its 'active and pending state' kept
in the *physical* distributor, and not in the virtual one, as mandated
by the spec (this is what allows the direct deactivation). The virtual
distributor only caries the pending and active *states* (note the
plural, as these are two independent and non-overlapping states).

Fix it by reading the HW state back, either from the timer itself or
from the distributor if necessary.

Reported-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
index 7068da080799..49837d3a3ef5 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio.c
@@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 						    IRQCHIP_STATE_PENDING,
 						    &val);
 			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
+		} else if (vgic_irq_is_mapped_level(irq)) {
+			val = vgic_get_phys_line_level(irq);
 		} else {
 			val = irq_is_pending(irq);
 		}
-- 
2.34.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
@ 2022-02-08 12:37 ` Marc Zyngier
  0 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2022-02-08 12:37 UTC (permalink / raw)
  To: linux-arm-kernel, kvmarm, kvm
  Cc: James Morse, Suzuki K Poulose, Alexandru Elisei, kernel-team,
	Ricardo Koller

It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
result in the pending interrupts being accurately reported if they are
mapped to a HW interrupt. This is particularily visible when acking
the timer interrupt and reading the GICR_ISPENDR1 register immediately
after, for example (the interrupt appears as not-pending while it really
is...).

This is because a HW interrupt has its 'active and pending state' kept
in the *physical* distributor, and not in the virtual one, as mandated
by the spec (this is what allows the direct deactivation). The virtual
distributor only caries the pending and active *states* (note the
plural, as these are two independent and non-overlapping states).

Fix it by reading the HW state back, either from the timer itself or
from the distributor if necessary.

Reported-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
index 7068da080799..49837d3a3ef5 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio.c
@@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 						    IRQCHIP_STATE_PENDING,
 						    &val);
 			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
+		} else if (vgic_irq_is_mapped_level(irq)) {
+			val = vgic_get_phys_line_level(irq);
 		} else {
 			val = irq_is_pending(irq);
 		}
-- 
2.34.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
@ 2022-02-08 12:37 ` Marc Zyngier
  0 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2022-02-08 12:37 UTC (permalink / raw)
  To: linux-arm-kernel, kvmarm, kvm
  Cc: James Morse, Suzuki K Poulose, Alexandru Elisei, kernel-team,
	Ricardo Koller

It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
result in the pending interrupts being accurately reported if they are
mapped to a HW interrupt. This is particularily visible when acking
the timer interrupt and reading the GICR_ISPENDR1 register immediately
after, for example (the interrupt appears as not-pending while it really
is...).

This is because a HW interrupt has its 'active and pending state' kept
in the *physical* distributor, and not in the virtual one, as mandated
by the spec (this is what allows the direct deactivation). The virtual
distributor only caries the pending and active *states* (note the
plural, as these are two independent and non-overlapping states).

Fix it by reading the HW state back, either from the timer itself or
from the distributor if necessary.

Reported-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
index 7068da080799..49837d3a3ef5 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio.c
@@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 						    IRQCHIP_STATE_PENDING,
 						    &val);
 			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
+		} else if (vgic_irq_is_mapped_level(irq)) {
+			val = vgic_get_phys_line_level(irq);
 		} else {
 			val = irq_is_pending(irq);
 		}
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
  2022-02-08 12:37 ` Marc Zyngier
  (?)
@ 2022-02-08 17:29   ` Ricardo Koller
  -1 siblings, 0 replies; 6+ messages in thread
From: Ricardo Koller @ 2022-02-08 17:29 UTC (permalink / raw)
  To: Marc Zyngier
  Cc: linux-arm-kernel, kvmarm, kvm, James Morse, Suzuki K Poulose,
	Alexandru Elisei, kernel-team

On Tue, Feb 08, 2022 at 12:37:26PM +0000, Marc Zyngier wrote:
> It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
> result in the pending interrupts being accurately reported if they are
> mapped to a HW interrupt. This is particularily visible when acking
> the timer interrupt and reading the GICR_ISPENDR1 register immediately
> after, for example (the interrupt appears as not-pending while it really
> is...).
> 
> This is because a HW interrupt has its 'active and pending state' kept
> in the *physical* distributor, and not in the virtual one, as mandated
> by the spec (this is what allows the direct deactivation). The virtual
> distributor only caries the pending and active *states* (note the
> plural, as these are two independent and non-overlapping states).
> 
> Fix it by reading the HW state back, either from the timer itself or
> from the distributor if necessary.
> 
> Reported-by: Ricardo Koller <ricarkol@google.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
> index 7068da080799..49837d3a3ef5 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio.c
> @@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  						    IRQCHIP_STATE_PENDING,
>  						    &val);
>  			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
> +		} else if (vgic_irq_is_mapped_level(irq)) {
> +			val = vgic_get_phys_line_level(irq);
>  		} else {
>  			val = irq_is_pending(irq);
>  		}
> -- 
> 2.34.1
> 

Thanks Marc!

Tested this fix with a selftest that we are planning to upstream soon.
It fires and handles arch timer IRQs while checking the pending state
along the way.

Tested-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
@ 2022-02-08 17:29   ` Ricardo Koller
  0 siblings, 0 replies; 6+ messages in thread
From: Ricardo Koller @ 2022-02-08 17:29 UTC (permalink / raw)
  To: Marc Zyngier; +Cc: kvm, kernel-team, kvmarm, linux-arm-kernel

On Tue, Feb 08, 2022 at 12:37:26PM +0000, Marc Zyngier wrote:
> It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
> result in the pending interrupts being accurately reported if they are
> mapped to a HW interrupt. This is particularily visible when acking
> the timer interrupt and reading the GICR_ISPENDR1 register immediately
> after, for example (the interrupt appears as not-pending while it really
> is...).
> 
> This is because a HW interrupt has its 'active and pending state' kept
> in the *physical* distributor, and not in the virtual one, as mandated
> by the spec (this is what allows the direct deactivation). The virtual
> distributor only caries the pending and active *states* (note the
> plural, as these are two independent and non-overlapping states).
> 
> Fix it by reading the HW state back, either from the timer itself or
> from the distributor if necessary.
> 
> Reported-by: Ricardo Koller <ricarkol@google.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
> index 7068da080799..49837d3a3ef5 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio.c
> @@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  						    IRQCHIP_STATE_PENDING,
>  						    &val);
>  			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
> +		} else if (vgic_irq_is_mapped_level(irq)) {
> +			val = vgic_get_phys_line_level(irq);
>  		} else {
>  			val = irq_is_pending(irq);
>  		}
> -- 
> 2.34.1
> 

Thanks Marc!

Tested this fix with a selftest that we are planning to upstream soon.
It fires and handles arch timer IRQs while checking the pending state
along the way.

Tested-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW
@ 2022-02-08 17:29   ` Ricardo Koller
  0 siblings, 0 replies; 6+ messages in thread
From: Ricardo Koller @ 2022-02-08 17:29 UTC (permalink / raw)
  To: Marc Zyngier
  Cc: linux-arm-kernel, kvmarm, kvm, James Morse, Suzuki K Poulose,
	Alexandru Elisei, kernel-team

On Tue, Feb 08, 2022 at 12:37:26PM +0000, Marc Zyngier wrote:
> It appears that a read access to GIC[DR]_I[CS]PENDRn doesn't always
> result in the pending interrupts being accurately reported if they are
> mapped to a HW interrupt. This is particularily visible when acking
> the timer interrupt and reading the GICR_ISPENDR1 register immediately
> after, for example (the interrupt appears as not-pending while it really
> is...).
> 
> This is because a HW interrupt has its 'active and pending state' kept
> in the *physical* distributor, and not in the virtual one, as mandated
> by the spec (this is what allows the direct deactivation). The virtual
> distributor only caries the pending and active *states* (note the
> plural, as these are two independent and non-overlapping states).
> 
> Fix it by reading the HW state back, either from the timer itself or
> from the distributor if necessary.
> 
> Reported-by: Ricardo Koller <ricarkol@google.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
> index 7068da080799..49837d3a3ef5 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio.c
> @@ -248,6 +248,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  						    IRQCHIP_STATE_PENDING,
>  						    &val);
>  			WARN_RATELIMIT(err, "IRQ %d", irq->host_irq);
> +		} else if (vgic_irq_is_mapped_level(irq)) {
> +			val = vgic_get_phys_line_level(irq);
>  		} else {
>  			val = irq_is_pending(irq);
>  		}
> -- 
> 2.34.1
> 

Thanks Marc!

Tested this fix with a selftest that we are planning to upstream soon.
It fires and handles arch timer IRQs while checking the pending state
along the way.

Tested-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-02-08 17:31 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-08 12:37 [PATCH] KVM: arm64: vgic: Read HW interrupt pending state from the HW Marc Zyngier
2022-02-08 12:37 ` Marc Zyngier
2022-02-08 12:37 ` Marc Zyngier
2022-02-08 17:29 ` Ricardo Koller
2022-02-08 17:29   ` Ricardo Koller
2022-02-08 17:29   ` Ricardo Koller

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