linux-kernel - Re: [PATCH v2 2/2] x86/sev-es: Invalidate the GHCB after completing VMGEXIT

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Date:   Tue, 18 May 2021 11:03:23 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Brijesh Singh <brijesh.singh@....com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] x86/sev-es: Invalidate the GHCB after completing
 VMGEXIT

On Mon, May 17, 2021 at 12:42:33PM -0500, Tom Lendacky wrote:
> Since the VMGEXIT instruction can be issued from userspace, invalidate
> the GHCB after performing VMGEXIT processing in the kernel.
> 
> Invalidation is only required after userspace is available, so call
> vc_ghcb_invalidate() from sev_es_put_ghcb(). Update vc_ghcb_invalidate()
> to additionally clear the GHCB exit code, so that a value of 0 is always
> present outside VMGEXIT processing in the kernel.
> 
> Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
> Cc: stable@...r.kernel.org
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>

Reviewed-by: Joerg Roedel <jroedel@...e.de>