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Date:   Fri, 4 Mar 2022 09:43:39 -0600
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Cc:     brijesh.singh@amd.com, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.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>,
        Borislav Petkov <bp@alien8.de>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        brijesh.ksingh@gmail.com, tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v11 42/45] virt: Add SEV-SNP guest driver
Content-Language: en-US
To:     Dave Hansen <dave.hansen@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org
References: <20220224165625.2175020-1-brijesh.singh@amd.com>
 <20220224165625.2175020-43-brijesh.singh@amd.com>
 <c85259c5-996c-902b-42b6-6b812282ee25@intel.com>
 <9c075b36-e450-831b-0ae2-3b680686beb4@amd.com>
 <bd52a9ed-c44f-989f-60a0-f15dd4260e09@intel.com>
From:   Brijesh Singh <brijesh.singh@amd.com>
In-Reply-To: <bd52a9ed-c44f-989f-60a0-f15dd4260e09@intel.com>
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On 3/4/22 9:23 AM, Dave Hansen wrote:
> On 3/4/22 05:17, Brijesh Singh wrote:
>>> BTW, this look like a generic allocator thingy.  But it's only ever used
>>> to allocate a 'struct snp_guest_msg'.  Why all the trouble to allocate
>>> and free one fixed-size structure?  The changelog and comments don't
>>> shed any light.
>> The GHCB specification says that a guest must use shared memory for
>> request, response, and certificate blob. In this patch, you are seeing
>> that {alloc,free}_shared_pages() used only to alloc/free the request and
>> response page. In the last patch, we used the same generic function to
>> allocate the certificate blob with a different size (~16K) than 'struct
>> snp_guest_msg.'
> It sounds like it's worth a sentence or two in the changelog to explain
> this new "allocator" and its future uses.

Will do.