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-sta...@nongnu.org
Signed-off-by: Peter Maydell <peter.mayd...@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(-)
diff --git a/hw/intc/arm_gicv3_cpuif.c b/hw/intc/arm_gicv3_cpuif.c
index ab1a00508e6..258dee1b808 100644
--- a/hw/intc/arm_gicv3_cpuif.c
+++ b/hw/intc/arm_gicv3_cpuif.c
@@ -1434,16 +1434,25 @@ static void icv_eoir_write(CPUARMState *env, const
ARMCPRegInfo *ri,
idx = icv_find_active(cs, irq);
if (idx < 0) {
- /* No valid list register corresponding to EOI ID */
- icv_increment_eoicount(cs);
+ /*
+ * No valid list register corresponding to EOI ID; if this is a vLPI
+ * not in the list regs then do nothing; otherwise increment EOI count
+ */
+ if (irq < GICV3_LPI_INTID_START) {
+ icv_increment_eoicount(cs);
+ }
} else {
uint64_t lr = cs->ich_lr_el2[idx];
int thisgrp = (lr & ICH_LR_EL2_GROUP) ? GICV3_G1NS : GICV3_G0;
int lr_gprio = ich_lr_prio(lr) & icv_gprio_mask(cs, grp);
if (thisgrp == grp && lr_gprio == dropprio) {
- if (!icv_eoi_split(env, cs)) {
- /* Priority drop and deactivate not split: deactivate irq now
*/
+ if (!icv_eoi_split(env, cs) || irq >= GICV3_LPI_INTID_START) {
+ /*
+ * Priority drop and deactivate not split: deactivate irq now.
+ * LPIs always get their active state cleared immediately
+ * because no separate deactivate is expected.
+ */
icv_deactivate_irq(cs, idx);
}
}
--
2.34.1
