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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id n6sm23363563pgb.60.2021.07.19.13.24.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jul 2021 13:24:49 -0700 (PDT) Date: Mon, 19 Jul 2021 20:24:45 +0000 From: Sean Christopherson To: Brijesh Singh Cc: 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, linux-crypto@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , tony.luck@intel.com, npmccallum@redhat.com, brijesh.ksingh@gmail.com Subject: Re: [PATCH Part2 RFC v4 22/40] KVM: SVM: Add KVM_SNP_INIT command Message-ID: References: <20210707183616.5620-1-brijesh.singh@amd.com> <20210707183616.5620-23-brijesh.singh@amd.com> <3f12243a-dee3-2a97-9a1b-51f4f6095349@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3f12243a-dee3-2a97-9a1b-51f4f6095349@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Fri, Jul 16, 2021, Brijesh Singh wrote: > > On 7/16/21 2:33 PM, Sean Christopherson wrote: > > On Wed, Jul 07, 2021, Brijesh Singh wrote: > >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > >> index 3fd9a7e9d90c..989a64aa1ae5 100644 > >> --- a/include/uapi/linux/kvm.h > >> +++ b/include/uapi/linux/kvm.h > >> @@ -1678,6 +1678,9 @@ enum sev_cmd_id { > >> /* Guest Migration Extension */ > >> KVM_SEV_SEND_CANCEL, > >> > >> + /* SNP specific commands */ > >> + KVM_SEV_SNP_INIT = 256, > > Is there any meaning behind '256'? If not, why skip a big chunk? I wouldn't be > > concerned if it weren't for KVM_SEV_NR_MAX, whose existence arguably implies that > > 0-KVM_SEV_NR_MAX-1 are all valid SEV commands. > > In previous patches, Peter highlighted that we should keep some gap > between the SEV/ES and SNP to leave room for legacy SEV/ES expansion. I > was not sure how many we need to reserve without knowing what will come > in the future; especially recently some of the command additional  are > not linked to the firmware. I am okay to reduce the gap or remove the > gap all together. Unless the numbers themselves have meaning, which I don't think they do, I vote to keep the arbitrary numbers contiguous. KVM_SEV_NR_MAX makes me nervous, and there are already cases of related commands being discontiguous, e.g. KVM_SEND_CANCEL. Peter or Paolo, any thoughts?