On Sun, 2022-02-20 at 20:19 -0600, Suravee Suthikulpanit wrote:
> Currently, AVIC is inactive when booting a VM w/ x2APIC support.
> With x2AVIC support, the APICV_INHIBIT_REASON_X2APIC can be removed.
The commit title is a bit misleading - the inhibit reason is not removed,
but rather AVIC is not inhibited when x2avic is present.
>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> ---
> 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 3306b74f1d8b..874c89f8fd47 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"
> @@ -176,6 +177,26 @@ 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);
BTW, now that I am thinking about it, it would be nice to be able to force
the AVIC_MODE_X1 even if x2avic is present, for debug purposes from a module
param. Just a suggestion.
> +}
> +
> 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 afca26aa1f40..b7bc6cd74aba 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3992,23 +3992,9 @@ 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 41514df5107e..aea80abe9186 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -578,6 +578,7 @@ void avic_update_vapic_bar(struct vcpu_svm *svm, u64 data);
> 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);
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
