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@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
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
