The hypervisor can deliver (virtual) LPIs to a guest by setting up a
list register to have an intid which is an LPI. The GIC has to treat
these a little differently to standard interrupt IDs, because LPIs
have no Active state, and so the guest will only EOI them, it will
not also deactivate them. So icv_eoir_write() must do two things:
* if the LPI ID is not in any list register, we drop the
priority but do not increment the EOI count
* if the LPI ID is in a list register, we immediately deactivate
it, regardless of the split-drop-and-deactivate control
This can be seen in the VirtualWriteEOIR0() and VirtualWriteEOIR1()
pseudocode in the GICv3 architecture specification.
Without this fix, potentially a hypervisor guest might stall because
LPIs get stuck in a bogus Active+Pending state.
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Weirdly, I only saw this being a problem when the hypervisor guest
was an EL2-enabled one under my FEAT_NV/FEAT_NV2 implementation.
But there's nothing FEAT_NV specific about the bug.
---
hw/intc/arm_gicv3_cpuif.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)