If APICv is inhibited, then IPIs from peer vCPUs are done by
atomically setting bits in IRR.
This means, that when __kvm_apic_update_irr copies PIR to IRR,
it has to modify IRR atomically as well.
Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 113ca9661ab21d..b17b37e4d4fcd1 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -637,16 +637,22 @@ bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr)
*max_irr = -1;
for (i = vec = 0; i <= 7; i++, vec += 32) {
+ u32 *p_irr = (u32 *)(regs + APIC_IRR + i * 0x10);
+
+ irr_val = *p_irr;
pir_val = READ_ONCE(pir[i]);
- irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10));
+
if (pir_val) {
+ pir_val = xchg(&pir[i], 0);
+
prev_irr_val = irr_val;
- irr_val |= xchg(&pir[i], 0);
- *((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val;
- if (prev_irr_val != irr_val) {
- max_updated_irr =
- __fls(irr_val ^ prev_irr_val) + vec;
- }
+ do {
+ irr_val = prev_irr_val | pir_val;
+ } while (prev_irr_val != irr_val &&
+ !try_cmpxchg(p_irr, &prev_irr_val, irr_val));
+
+ if (prev_irr_val != irr_val)
+ max_updated_irr = __fls(irr_val ^ prev_irr_val) + vec;
}
if (irr_val)
*max_irr = __fls(irr_val) + vec;
--
2.26.3
