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Subject[RFCv2 PATCH 12/12] KVM: SVM: Do not inhibit APICv when x2APIC is present
Date
Currently, AVIC is inhibited when booting a VM w/ x2APIC support.
This is because AVIC cannot virtualize x2APIC mode in the VM.
With x2AVIC support, the APICV_INHIBIT_REASON_X2APIC is
no longer enforced.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
arch/x86/kvm/svm/avic.c | 21 +++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 18 ++----------------
arch/x86/kvm/svm/svm.h | 1 +
3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 015888aad8fc..e4bf4f68f332 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -21,6 +21,7 @@

#include <asm/irq_remapping.h>

+#include "cpuid.h"
#include "trace.h"
#include "lapic.h"
#include "x86.h"
@@ -159,6 +160,26 @@ void avic_vm_destroy(struct kvm *kvm)
spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);
}

+void avic_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu, int nested)
+{
+ /*
+ * If the X2APIC feature is exposed to the guest,
+ * disable AVIC unless X2AVIC mode is enabled.
+ */
+ if (avic_mode == AVIC_MODE_X1 &&
+ guest_cpuid_has(vcpu, X86_FEATURE_X2APIC))
+ kvm_request_apicv_update(vcpu->kvm, false,
+ APICV_INHIBIT_REASON_X2APIC);
+
+ /*
+ * Currently, AVIC does not work with nested virtualization.
+ * So, we disable AVIC when cpuid for SVM is set in the L1 guest.
+ */
+ if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM))
+ kvm_request_apicv_update(vcpu->kvm, false,
+ APICV_INHIBIT_REASON_NESTED);
+}
+
int avic_vm_init(struct kvm *kvm)
{
unsigned long flags;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ce3c68a785cf..01384ccdb56c 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3988,23 +3988,9 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
vcpu->arch.reserved_gpa_bits &= ~(1UL << (best->ebx & 0x3f));
}

- if (kvm_vcpu_apicv_active(vcpu)) {
- /*
- * AVIC does not work with an x2APIC mode guest. If the X2APIC feature
- * is exposed to the guest, disable AVIC.
- */
- if (guest_cpuid_has(vcpu, X86_FEATURE_X2APIC))
- kvm_request_apicv_update(vcpu->kvm, false,
- APICV_INHIBIT_REASON_X2APIC);
+ if (kvm_vcpu_apicv_active(vcpu))
+ avic_vcpu_after_set_cpuid(vcpu, nested);

- /*
- * Currently, AVIC does not work with nested virtualization.
- * So, we disable AVIC when cpuid for SVM is set in the L1 guest.
- */
- if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM))
- kvm_request_apicv_update(vcpu->kvm, false,
- APICV_INHIBIT_REASON_NESTED);
- }
init_vmcb_after_set_cpuid(vcpu);
}

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 19ad40b8383b..30fd9c8da9f2 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -576,6 +576,7 @@ int avic_init_vcpu(struct vcpu_svm *svm);
void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
void avic_vcpu_put(struct kvm_vcpu *vcpu);
void avic_post_state_restore(struct kvm_vcpu *vcpu);
+void avic_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu, int nested);
void svm_set_virtual_apic_mode(struct kvm_vcpu *vcpu);
void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu);
bool svm_check_apicv_inhibit_reasons(ulong bit);
--
2.25.1
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