[v2] AMD: Add Secure AVIC KVM Support

[RFC PATCH v2 10/17] KVM: SVM: Set VGIF in VMSA area for Secure AVIC guests

Posted by Neeraj Upadhyay 1 week, 1 day ago

From: Kishon Vijay Abraham I <kvijayab@amd.com>

Unlike standard SVM which uses the V_GIF (Virtual Global Interrupt Flag)
bit in the VMCB, Secure AVIC ignores this field.

Instead, the hardware requires an equivalent V_GIF bit to be set within
the vintr_ctrl field of the VMSA (Virtual Machine Save Area). Failure
to set this bit will cause the hardware to block all interrupt delivery,
rendering the guest non-functional.

To enable interrupts for Secure AVIC guests, modify sev_es_sync_vmsa()
to unconditionally set the V_GIF_MASK in the VMSA's vintr_ctrl field
whenever Secure AVIC is active. This ensures the hardware correctly
identifies the guest as interruptible.

Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
---
 arch/x86/kvm/svm/sev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 837ab55a3330..2dee210efb37 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -884,6 +884,9 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
 
 	save->sev_features = sev->vmsa_features;
 
+	if (sev_savic_active(vcpu->kvm))
+		save->vintr_ctrl |= V_GIF_MASK;
+
 	/*
 	 * Skip FPU and AVX setup with KVM_SEV_ES_INIT to avoid
 	 * breaking older measurements.
-- 
2.34.1

Re: [RFC PATCH v2 10/17] KVM: SVM: Set VGIF in VMSA area for Secure AVIC guests

Posted by Tom Lendacky 1 week, 1 day ago

On 9/23/25 00:03, Neeraj Upadhyay wrote:
> From: Kishon Vijay Abraham I <kvijayab@amd.com>
> 
> Unlike standard SVM which uses the V_GIF (Virtual Global Interrupt Flag)
> bit in the VMCB, Secure AVIC ignores this field.
> 
> Instead, the hardware requires an equivalent V_GIF bit to be set within
> the vintr_ctrl field of the VMSA (Virtual Machine Save Area). Failure
> to set this bit will cause the hardware to block all interrupt delivery,
> rendering the guest non-functional.
> 
> To enable interrupts for Secure AVIC guests, modify sev_es_sync_vmsa()
> to unconditionally set the V_GIF_MASK in the VMSA's vintr_ctrl field
> whenever Secure AVIC is active. This ensures the hardware correctly
> identifies the guest as interruptible.
> 
> Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
> Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> ---
>  arch/x86/kvm/svm/sev.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 837ab55a3330..2dee210efb37 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -884,6 +884,9 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
>  
>  	save->sev_features = sev->vmsa_features;
>  
> +	if (sev_savic_active(vcpu->kvm))
> +		save->vintr_ctrl |= V_GIF_MASK;

A comment above this would be good.

Thanks,
Tom

> +
>  	/*
>  	 * Skip FPU and AVX setup with KVM_SEV_ES_INIT to avoid
>  	 * breaking older measurements.