[PATCH 1/2] KVM: VMX: Do not fully reset PI descriptor on vCPU reset

[PATCH 1/2] KVM: VMX: Do not fully reset PI descriptor on vCPU reset

[Jan H. Schönherr]

Parts of the posted interrupt descriptor configure host behavior,
such as the notification vector and destination. Overwriting them
with zero as done during vCPU reset breaks posted interrupts.
KVM (re-)writes these fields on certain occasions and belatedly fixes
the situation in many cases. However, if you have a guest configured
with "idle=poll", for example, the fields might stay zero forever.

Do not reset the full descriptor in vmx_vcpu_reset(). Instead,
reset only the outstanding notifications and leave everything
else untouched.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
---
 arch/x86/kvm/vmx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e6c8ffa..2e008e4 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5618,8 +5618,10 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 
 	kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
 
-	if (kvm_vcpu_apicv_active(vcpu))
-		memset(&vmx->pi_desc, 0, sizeof(struct pi_desc));
+	if (kvm_vcpu_apicv_active(vcpu)) {
+		pi_clear_on(&vmx->pi_desc);
+		memset(vmx->pi_desc.pir, 0, sizeof(vmx->pi_desc.pir));
+	}
 
 	if (vmx->vpid != 0)
 		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
-- 
2.3.1.dirty

[PATCH 2/2] KVM: x86: Update APICv on APIC reset

[Jan H. Schönherr]

In kvm_apic_set_state() we update the hardware virtualized APIC after
the full APIC state has been overwritten. Do the same, when the full
APIC state has been reset in kvm_lapic_reset().

This updates some hardware state that was previously forgotten, as
far as I can tell. Also, this allows removing some APIC-related reset
code from vmx_vcpu_reset().

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
---
 arch/x86/kvm/lapic.c | 5 +++++
 arch/x86/kvm/vmx.c   | 5 -----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index a778f1a..943acbf 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2041,6 +2041,11 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
 				vcpu->arch.apic_base | MSR_IA32_APICBASE_BSP);
 	vcpu->arch.pv_eoi.msr_val = 0;
 	apic_update_ppr(apic);
+	if (vcpu->arch.apicv_active) {
+		kvm_x86_ops->apicv_post_state_restore(vcpu);
+		kvm_x86_ops->hwapic_irr_update(vcpu, -1);
+		kvm_x86_ops->hwapic_isr_update(vcpu, -1);
+	}
 
 	vcpu->arch.apic_arb_prio = 0;
 	vcpu->arch.apic_attention = 0;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2e008e4..7c3522a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5618,11 +5618,6 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 
 	kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
 
-	if (kvm_vcpu_apicv_active(vcpu)) {
-		pi_clear_on(&vmx->pi_desc);
-		memset(vmx->pi_desc.pir, 0, sizeof(vmx->pi_desc.pir));
-	}
-
 	if (vmx->vpid != 0)
 		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
 
-- 
2.3.1.dirty