Commit 5bfa685e authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: vgic: Read HW interrupt pending state from the HW 



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: default avatarRicardo Koller <ricarkol@google.com>
Tested-by: default avatarRicardo Koller <ricarkol@google.com>
Reviewed-by: default avatarRicardo Koller <ricarkol@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220208123726.3604198-1-maz@kernel.org
parent 1dd498e5

arch/arm64/kvm/vgic/vgic-mmio.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

		}