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Peter Anvin" , "linux-kernel@vger.kernel.org" , "Lendacky, Thomas" , Andy Lutomirski Subject: Re: [PATCH v2] KVM: SVM: use vmsave/vmload for saving/restoring additional host state Message-ID: <20201216170740.d73xomotx4c3oxql@amd.com> References: <20201214220213.np7ytcxmm6xcyllm@amd.com> <98F09A9A-A768-4B01-A1FA-5EE681146BC5@amacapital.net> <20201215181747.jhozec5gpa4ud5qt@amd.com> <20201216151203.utpaitooaer7mdfa@amd.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Originating-IP: [165.204.11.250] X-ClientProxiedBy: MN2PR20CA0018.namprd20.prod.outlook.com (2603:10b6:208:e8::31) To CH2PR12MB4133.namprd12.prod.outlook.com (2603:10b6:610:7a::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from localhost (165.204.11.250) by MN2PR20CA0018.namprd20.prod.outlook.com (2603:10b6:208:e8::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3654.12 via Frontend Transport; Wed, 16 Dec 2020 17:07:47 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: 44478b30-d26a-46c7-91a8-08d8a1e51cf7 X-MS-TrafficTypeDiagnostic: CH2PR12MB4213: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: T26tNXrmhokciZJyyOaf1SraTFqFtPKRI0LNWI+b7Pgin8r7j4OFra7qr0CxGCIYvdsnrgBmmjKkt0PeeDTJyUzri0wara0NYtPwd9oNEYRf9enAURLRCsddegdrnHHE77oT2P1nKup9Fh15sgIyC85YE6BZ+9YzCeXwNyRLTZmkts+yFH5mcmK9YBpXT4Hk/P8GqBRqb7QQg0N5MMLqXdypsBAIqwkgLYF0ZjGF3AW38NVCPIoLjfEpXv40/PFWa4Zapz6rn4BGrvrkq/1LBoZiYnXafjWNLO4QObMTaOTb+Lvf1/1w1uXlb2UaHcx5 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH2PR12MB4133.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(376002)(136003)(396003)(39860400002)(366004)(346002)(54906003)(478600001)(36756003)(66946007)(52116002)(8936002)(6486002)(44832011)(6666004)(2906002)(1076003)(186003)(4326008)(16526019)(2616005)(66556008)(316002)(26005)(53546011)(6496006)(6916009)(5660300002)(7416002)(86362001)(956004)(8676002)(66476007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?kyhuQ5o+Nqo5NH9J8A9OOdOkFgCCZvDBk0HSa4cPehv1kx36b/hs3tJeVbD5?= =?us-ascii?Q?qVDwxPTJZZ8aNUjrya/ggxll2zqULvyt+FcV15awt+yWQO4gFl/n7BLUjGZA?= =?us-ascii?Q?WZvX6QmYq0r/AgGCa4KAs+WGB3doHt4J/foLf63ozUFXZcjCJfnXOzOmL902?= =?us-ascii?Q?oVvIvZRdxYyMZH0ylkqtcBKOTBDV3A4H8vJgM5fx1R8sgDIVOVYj6PBbzIh+?= =?us-ascii?Q?KeQ3vYokPmD8oS+oX9OrMgDjGFYHopLayJzRTMKLqQU/xksYtqRHxFOcGcdX?= =?us-ascii?Q?/WaLzIvUpGH3AhXnmGIGGEzAuxGT4vRGhQQja3j/Nx3soZgkiYlMcygh9hIw?= =?us-ascii?Q?bR1CNyUzhvAXl8sCJvQJStTUOTrtpU43mO6PLDlsuDuH4qwDfyIx72MDg+AE?= =?us-ascii?Q?gx5KXy1H65YY9Eah0lqpzq0PGjrYJhsOwib12Cn4V9FoxEcuOAHcbABnd7Qf?= =?us-ascii?Q?f9M9KEnJ4IUTOWiiQkj8SwnS3WpumyBvts0fV2ZAFrvAc8eNhBlD3iz4LpGl?= =?us-ascii?Q?lJr3wBKWEMTM83vXPe6SJ+I05P0E32X0U77fd2OeAyz9Kj+fysg7C1TolsQ0?= =?us-ascii?Q?pr2TkNK1g85zgx6VT0dbVuu7MRjOGzO2pG5n69fSdhd7UT9mWglQqJCdvWHp?= =?us-ascii?Q?K9Dgb5Pb8V11uGMLwID0V7RXmWZN5vYhOtIZ1EBiMcXcWww62wru6tpHSn3q?= =?us-ascii?Q?bqd294kvGZK/plLcuONb+thA+q1hdE89F4XSEoAolWjrVnKkBlW0gO0MOlVY?= =?us-ascii?Q?eZl7EQC11CYaMY63gIQR0pmyNrw67t5nYeoUVj34D5HWRtf0q/sF3ym6is2o?= =?us-ascii?Q?1tLn4kbghiWSRS1xbMXUvBLsIrfCr20KIhBFIFL2YnKWtByhzE5LV2WwcofI?= =?us-ascii?Q?ciMfveOlPp55CugxAPKIolI6FbGPiNQv6izYFaHyque3Ug7dqO7r7s4aRfHH?= =?us-ascii?Q?DFIuIm2dyLw7cdDTRmsyAt2nKLtGsNK0VAHP1G119GmLvdugSypgMkJ7o1kp?= =?us-ascii?Q?hRCe?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-AuthSource: CH2PR12MB4133.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Dec 2020 17:07:47.8086 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-Network-Message-Id: 44478b30-d26a-46c7-91a8-08d8a1e51cf7 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 0Vyx652DLpk/r+BEnnIdJqL869U1zfAFqwEYgEAujh5WmjZB5uZfE3vkX7cRjWBh/V81WlRDszqAzPRBDIaGiQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4213 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 16, 2020 at 04:23:22PM +0100, Paolo Bonzini wrote: > On 16/12/20 16:12, Michael Roth wrote: > > It looks like it does save us ~20-30 cycles vs. vmload, but maybe not > > enough to justify the added complexity. Additionally, since we still > > need to call vmload when we exit to userspace, it ends up being a bit > > slower for this particular workload at least. So for now I'll plan on > > sticking to vmload'ing after vmexit and moving that to the asm code > > if there are no objections. > > Yeah, agreed. BTW you can use "./x86/run x86/vmexit.flat" from > kvm-unit-tests to check the numbers for a wide range of vmexit paths. Wasn't aware of that, this looks really useful. Thanks! > > Paolo > > > current v2 patch, sample 1 > > ioctl entry: 1204722748832 > > pre-run: 1204722749408 ( +576) > > post-run: 1204722750784 (+1376) > > ioctl exit: 1204722751360 ( +576) > > total cycles: 2528 > > > > current v2 patch, sample 2 > > ioctl entry: 1204722754784 > > pre-vmrun: 1204722755360 ( +576) > > post-vmrun: 1204722756720 (+1360) > > ioctl exit: 1204722757312 ( +592) > > total cycles 2528 > > > > wrgsbase, sample 1 > > ioctl entry: 1346624880336 > > pre-vmrun: 1346624880912 ( +576) > > post-vmrun: 1346624882256 (+1344) > > ioctl exit: 1346624882912 ( +656) > > total cycles 2576 > > > > wrgsbase, sample 2 > > ioctl entry: 1346624886272 > > pre-vmrun: 1346624886832 ( +560) > > post-vmrun: 1346624888176 (+1344) > > ioctl exit: 1346624888816 ( +640) > > total cycles: 2544 > > >