KVM: x86: Do not change ICR on write to APIC_SELF_IPI

BugLink: https://bugs.launchpad.net/bugs/1978240
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 4d92fb4fdf69989770651ae54c971581822caee4..83d1743a1dd0ad4f09deb024cf25642e1f100ec5 100644 (file)
--- 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: