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Peter Anvin" , Paolo Bonzini , Sean Christopherson , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active To: 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> <20180910155329.GB20286@zn.tnic> From: Brijesh Singh Message-ID: <564fd92f-04b5-d28c-03a3-59d11ab4c6cd@amd.com> Date: Mon, 10 Sep 2018 11:14:10 -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: <20180910155329.GB20286@zn.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [165.204.77.1] X-ClientProxiedBy: SN4PR0501CA0065.namprd05.prod.outlook.com (2603:10b6:803:41::42) To DM6PR12MB2682.namprd12.prod.outlook.com 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X-Microsoft-Exchange-Diagnostics: 1;DM6PR12MB2682;20:m9HHX/s61+EDIzFXczu6EWTGKdL/sS4JTfH268wRliv2uHRvORduShDr00IzGRWziTJFJpUoDPPcbju7yYj1DeQ59rTsAza6XN2RBzzCpURM/nlNIQV/lddxdAJBW6mjxJ+pgNeIcUaH8gne0SFvMbkPJONKqcl3emuLvyu9guDqrYhogwRBGB5VwEzNVxu/G8u/nc0tep07C6hkg0+gHbXS8RKxPVJDOdEh8cZIzHyxZmA/mYU8InEkxJgy5hLp X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Sep 2018 16:14:13.3365 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a0b55a13-b09a-4aab-eebb-08d61738734f X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB2682 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/10/2018 10:53 AM, Borislav Petkov wrote: > On Mon, Sep 10, 2018 at 08:15:38AM -0500, Brijesh Singh wrote: >>> Now, the real question from all this SNAFU is, why can't all those point >>> to a single struct pvclock_vsyscall_time_info and all CPUs read a single >>> thing? Why do they have to be per-CPU and thus waste so much memory? > > You forgot to answer to the real question - why do we need those things > to be perCPU and why can't we use a single instance to share with *all* > CPUs? > > Because if we can, then we're golden! > I did not forgot to answer it. Maybe Paolo or someone more knowledgeable in that area of code can comment why those are perCpu. -Brijesh