Re: [PATCH] nestedsvm: Clear GIF when injecting VMEXIT

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

Le 23/04/2026 à 18:13, Ross Lagerwall a écrit :
> If L1 executes VMRUN with the GIF set and it fails consistency checks,
> Xen will inject a VMEXIT and fail the assert checking the GIF is cleared.
> 
> Instead, clear the GIF when injecting a VMEXIT to match what hardware
> does.
> 
> Fixes: 9a779e4fc161 ("Implement SVM specific part for Nested Virtualization")
> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> ---
>   xen/arch/x86/hvm/svm/nestedsvm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c 
> b/xen/arch/x86/hvm/svm/nestedsvm.c
> index ef6fa5d23b67..f89b087a1155 100644
> --- a/xen/arch/x86/hvm/svm/nestedsvm.c
> +++ b/xen/arch/x86/hvm/svm/nestedsvm.c
> @@ -733,9 +733,9 @@ nsvm_vcpu_vmexit_inject(struct vcpu *v, struct 
> cpu_user_regs *regs,
>       struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
>   
>       if ( vmcb->_vintr.fields.vgif_enable )
> -        ASSERT(vmcb->_vintr.fields.vgif == 0);
> +        vmcb->_vintr.fields.vgif = 0;
>       else
> -        ASSERT(svm->ns_gif == 0);
> +        nestedsvm_vcpu_clgi(v);
>   
>       ns_vmcb = nv->nv_vvmcx;
>   

Looks good to me, though I think we are here looking to make a "guest 
CLGI" (clear GIF), so the vGIF specific logic should be collapsed into 
nestedsvm_vcpu_clgi() instead of having it as the non-vgif-support case.
(as IIUC, vGIF is a hardware accelration for nested GIF handling ?)

(also making me notice that svm_vmexit_do_{stgi,clgi}() seems to lack 
vGIF specific logic)

Teddy


--
Teddy Astie | Vates XCP-ng Developer

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