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svm: Deactivate AVIC when launching guest with nested SVM support 

Since AVIC does not currently work w/ nested virtualization,
deactivate AVIC for the guest if setting CPUID Fn80000001_ECX[SVM]
(i.e. indicate support for SVM, which is needed for nested virtualization).
Also, introduce a new APICV_INHIBIT_REASON_NESTED bit to be used for
this reason.

Suggested-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Suravee Suthikulpanit 2019-11-14 14:15:14 -06:00 committed by Paolo Bonzini
parent f4fdc0a2ed
commit 9a0bf05430
2 changed files with 11 additions and 1 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -877,6 +877,7 @@ enum kvm_irqchip_mode {
#define APICV_INHIBIT_REASON_DISABLE 0 #define APICV_INHIBIT_REASON_DISABLE 0
#define APICV_INHIBIT_REASON_HYPERV 1 #define APICV_INHIBIT_REASON_HYPERV 1
#define APICV_INHIBIT_REASON_NESTED 2
struct kvm_arch { struct kvm_arch {
unsigned long n_used_mmu_pages; unsigned long n_used_mmu_pages;

11
arch/x86/kvm/svm.c
View File

@ -5988,6 +5988,14 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
return; return;
guest_cpuid_clear(vcpu, X86_FEATURE_X2APIC); guest_cpuid_clear(vcpu, X86_FEATURE_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);
} }
#define F feature_bit #define F feature_bit
@ -7319,7 +7327,8 @@ static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
static bool svm_check_apicv_inhibit_reasons(ulong bit) static bool svm_check_apicv_inhibit_reasons(ulong bit)
{ {
ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) | ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) |
BIT(APICV_INHIBIT_REASON_HYPERV); BIT(APICV_INHIBIT_REASON_HYPERV) |
BIT(APICV_INHIBIT_REASON_NESTED);
return supported & BIT(bit); return supported & BIT(bit);
} }