linux-kernel - Re: [PATCH Part2 v5 34/45] KVM: SVM: Do not use long-lived GHCB map while setting scratch area

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Message-ID: <YWdNisk78f5BVNv3@google.com>
Date:   Wed, 13 Oct 2021 21:20:10 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 34/45] KVM: SVM: Do not use long-lived GHCB map
 while setting scratch area

On Fri, Aug 20, 2021, Brijesh Singh wrote:
> The setup_vmgexit_scratch() function may rely on a long-lived GHCB
> mapping if the GHCB shared buffer area was used for the scratch area.
> In preparation for eliminating the long-lived GHCB mapping, always
> allocate a buffer for the scratch area so it can be accessed without
> the GHCB mapping.

Would it make sense to post this patch and the next (Remove the long-lived GHCB
host map) in a separate mini-series?  It's needed for SNP, but AFAICT there's
nothing that depends on SNP.  Getting this merged ahead of time would reduce the
size of the SNP series by a smidge.