linux-kernel - Re: [PATCH 10/10] KVM: SVM: Invalidate "next" SNP VMSA GPA even on failure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aefcb575-b049-8a9f-b2f0-32333af00e07@amd.com>
Date: Mon, 24 Feb 2025 18:00:21 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Naveen N Rao <naveen@...nel.org>, Kim Phillips <kim.phillips@....com>,
 Alexey Kardashevskiy <aik@....com>
Subject: Re: [PATCH 10/10] KVM: SVM: Invalidate "next" SNP VMSA GPA even on
 failure

On 2/18/25 19:27, Sean Christopherson wrote:
> When processing an SNP AP Creation event, invalidate the "next" VMSA GPA
> even if acquiring the page/pfn for the new VMSA fails.  In practice, the
> next GPA will never be used regardless of whether or not its invalidated,
> as the entire flow is guarded by snp_ap_waiting_for_reset, and said guard
> and snp_vmsa_gpa are always written as a pair.  But that's really hard to
> see in the code.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/kvm/svm/sev.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 15c324b61b24..7345cac6f93a 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -3877,6 +3877,7 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
>  		return;
>  
>  	gfn = gpa_to_gfn(svm->sev_es.snp_vmsa_gpa);
> +	svm->sev_es.snp_vmsa_gpa = INVALID_PAGE;
>  
>  	slot = gfn_to_memslot(vcpu->kvm, gfn);
>  	if (!slot)
> @@ -3906,8 +3907,6 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
>  	/* Mark the vCPU as runnable */
>  	kvm_set_mp_state(vcpu, KVM_MP_STATE_RUNNABLE);
>  
> -	svm->sev_es.snp_vmsa_gpa = INVALID_PAGE;
> -
>  	/*
>  	 * gmem pages aren't currently migratable, but if this ever changes
>  	 * then care should be taken to ensure svm->sev_es.vmsa is pinned