Date:   Tue, 16 Nov 2021 14:30:14 +0100
From:   Joerg Roedel <jroedel@suse.de>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Marc Orr <marcorr@google.com>,
        "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@intel.com>,
        Peter Gonda <pgonda@google.com>,
        Brijesh Singh <brijesh.singh@amd.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        linux-crypto@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Tom Lendacky <Thomas.Lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Michael Roth <Michael.Roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>, tony.luck@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com,
        Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
        Quentin Perret <qperret@google.com>
Subject: Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP)
 Hypervisor Support
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References: <20210820155918.7518-1-brijesh.singh@amd.com>
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 <YY7FAW5ti7YMeejj@google.com>
 <YZJTA1NyLCmVtGtY@work-vm>
 <YZKmSDQJgCcR06nE@google.com>
 <CAA03e5E3Rvx0t8_ZrbNMZwBkjPivGKOg5HCShSFYwfkKDDHWtA@mail.gmail.com>
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On Mon, Nov 15, 2021 at 07:15:07PM +0000, Sean Christopherson wrote:
> It creates a new attack surface, e.g. if the guest mishandles the #VC and does
> PVALIDATE on memory that it previously accepted, then userspace can attack the
> guest by accessing guest private memory to coerce the guest into consuming corrupted
> data.

If a guest can be tricked into a double PVALIDATE or otherwise
misbehaves on a #VC exception, then it is a guest bug and needs to be
fixed there.

It is a core requirement to the #VC handler that it can not be tricked
that way.

Regards,

-- 
J?rg R?del
jroedel@suse.de

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