linux-kernel - Re: [PATCH] KVM: SVM: Don't set GIF when clearing EFER.SVME

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Message-ID: <lliivrmxbgxhovwdp7lg3dglyig7ql6fhs2ekufoxmvhfthd7m@3elodo2keern>
Date: Tue, 7 Oct 2025 23:39:25 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Jim Mattson <jmattson@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: SVM: Don't set GIF when clearing EFER.SVME

On Tue, Oct 07, 2025 at 03:44:00PM -0700, Jim Mattson wrote:
> Clearing EFER.SVME is not architected to set GIF. Don't set GIF when
> emulating a change to EFER that clears EFER.SVME.
> 
> This is covered in the discussion at
> https://lore.kernel.org/all/5b8787b8-16e9-13dc-7fca-0dc441d673f9@citrix.com/.
> 
> Fixes: c513f484c558 ("KVM: nSVM: leave guest mode when clearing EFER.SVME")
> Signed-off-by: Jim Mattson <jmattson@...gle.com>

Reviewed-by: Yosry Ahmed <yosry.ahmed@...ux.dev>

> ---
>  arch/x86/kvm/svm/svm.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 3a9fe0a8b78c..5387851a96da 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -223,7 +223,6 @@ int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
>  	if ((old_efer & EFER_SVME) != (efer & EFER_SVME)) {
>  		if (!(efer & EFER_SVME)) {
>  			svm_leave_nested(vcpu);
> -			svm_set_gif(svm, true);
>  			/* #GP intercept is still needed for vmware backdoor */
>  			if (!enable_vmware_backdoor)
>  				clr_exception_intercept(svm, GP_VECTOR);
> -- 
> 2.51.0.710.ga91ca5db03-goog
>