[PATCH MANUALSEL 5.17 4/7] KVM: x86: Do not change ICR on write to APIC_SELF_IPI

Sasha Levin
2022-04-27T15:54:45Z

From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit d22a81b304a27fca6124174a8e842e826c193466 ]

Emulating writes to SELF_IPI with a write to ICR has an unwanted side effect:
the value of ICR in vAPIC page gets changed. The lists SELF_IPI as write-only,
with no associated MMIO offset, so any write should have no visible side
effect in the vAPIC page.

Reported-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/lapic.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 2a10d0033c96..6b6f9359d29e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2125,10 +2125,9 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
break;

case APIC_SELF_IPI:
- if (apic_x2apic_mode(apic)) {
- kvm_lapic_reg_write(apic, APIC_ICR,
- APIC_DEST_SELF | (val & APIC_VECTOR_MASK));
- } else
+ if (apic_x2apic_mode(apic))
+ kvm_apic_send_ipi(apic, APIC_DEST_SELF | (val & APIC_VECTOR_MASK), 0);
+ else
ret = 1;
break;
default:
--
2.35.1