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Peter Anvin" , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active To: Sean Christopherson , Borislav Petkov References: <1536343050-18532-1-git-send-email-brijesh.singh@amd.com> <1536343050-18532-6-git-send-email-brijesh.singh@amd.com> <20180910122727.GE21815@zn.tnic> <026d5ca5-7b77-de6c-477e-ff39f0291ac0@amd.com> <1536586152.11460.40.camel@intel.com> <097eb5f5-2cd9-8b08-32c5-d90c8e0cbb6d@amd.com> <1536593297.11460.72.camel@intel.com> From: Brijesh Singh Message-ID: <11618b8b-4d1f-9307-35f0-3c0f0fc856ca@amd.com> Date: Mon, 10 Sep 2018 10:30:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1536593297.11460.72.camel@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [165.204.77.1] X-ClientProxiedBy: SN4PR0201CA0025.namprd02.prod.outlook.com (2603:10b6:803:2e::11) To DM6PR12MB2682.namprd12.prod.outlook.com (2603:10b6:5:4a::31) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: f370b684-25b6-4725-54ff-08d617325f21 X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989137)(4534165)(4627221)(201703031133081)(201702281549075)(8990107)(5600074)(711020)(4618075)(2017052603328)(7153060)(7193020);SRVR:DM6PR12MB2682; 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If count is greater than KVM_MAX_VCPUS then it will >> fail to launch guest (or fail to hot plug vcpus). In other words, the >> number of vcpus in a KVM guest will never to > KVM_MAX_VCPUS. >> >> Am I missing something ? > > KVM_MAX_VCPUS is a definition for use in the *host*, it's even defined > in kvm_host.h.  The guest's pvclock code won't get magically recompiled > if KVM_MAX_VCPUS is changed in the host.  KVM_MAX_VCPUS is an arbitrary > value in the sense that there isn't a fundamental hard limit, i.e. the > value can be changed, either for a custom KVM build or in mainline, > e.g. it was bumped in 2016: > Ah I see your point. thanks for clarifying it.