From: Marc Zyngier maz@kernel.org
[ Upstream commit 5bfa685e62e9ba93c303a9a8db646c7228b9b570 ]
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 Tested-by: Ricardo Koller ricarkol@google.com Reviewed-by: Ricardo Koller ricarkol@google.com Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20220208123726.3604198-1-maz@kernel.org Signed-off-by: Sasha Levin sashal@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 b2d73fc0d1ef4..9e1459534ce54 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); }