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Thu, 15 Jun 2023 01:40:40 -0500 From: Alexey Kardashevskiy To: CC: , , Tom Lendacky , Sean Christopherson , "Alexey Kardashevskiy" Subject: [PATCH kernel 3/9] KVM: SVM: Rewrite sev_es_prepare_switch_to_guest()'s comment about swap types Date: Thu, 15 Jun 2023 16:37:51 +1000 Message-ID: <20230615063757.3039121-4-aik@amd.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230615063757.3039121-1-aik@amd.com> References: <20230615063757.3039121-1-aik@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002529D:EE_|DM4PR12MB6637:EE_ X-MS-Office365-Filtering-Correlation-Id: a708e515-c8ff-450b-ac7e-08db6d6b71ba X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230028)(4636009)(39860400002)(136003)(396003)(346002)(376002)(451199021)(46966006)(40470700004)(36840700001)(36756003)(47076005)(478600001)(4326008)(6666004)(6916009)(54906003)(70206006)(316002)(70586007)(356005)(8676002)(5660300002)(82310400005)(40480700001)(8936002)(41300700001)(2616005)(2906002)(82740400003)(426003)(186003)(26005)(81166007)(1076003)(83380400001)(16526019)(36860700001)(336012)(40460700003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jun 2023 06:40:43.9419 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a708e515-c8ff-450b-ac7e-08db6d6b71ba X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002529D.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6637 X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,SPF_HELO_PASS, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1768751499092482484?= X-GMAIL-MSGID: =?utf-8?q?1768751499092482484?= From: Sean Christopherson Rewrite the comment(s) in sev_es_prepare_switch_to_guest() to explain the swap types employed by the CPU for SEV-ES guests, i.e. to explain why KVM needs to save a seemingly random subset of host state, and to provide a decoder for the APM's Type-A/B/C terminology. Signed-off-by: Sean Christopherson Signed-off-by: Alexey Kardashevskiy --- Changes: v6: * new to the series --- arch/x86/kvm/svm/sev.c | 25 ++++++++++++-------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index c03bd063aecf..36fe2fcb4698 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3020,19 +3020,24 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm) void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa) { /* - * As an SEV-ES guest, hardware will restore the host state on VMEXIT, - * of which one step is to perform a VMLOAD. KVM performs the - * corresponding VMSAVE in svm_prepare_guest_switch for both - * traditional and SEV-ES guests. + * All host state for SEV-ES guests is categorized into three swap types + * based on how it is handled by hardware during a world switch: + * + * A: VMRUN: Host state saved in host save area + * VMEXIT: Host state loaded from host save area + * + * B: VMRUN: Host state _NOT_ saved in host save area + * VMEXIT: Host state loaded from host save area + * + * C: VMRUN: Host state _NOT_ saved in host save area + * VMEXIT: Host state initialized to default(reset) values + * + * Manually save type-B state, i.e. state that is loaded by VMEXIT but + * isn't saved by VMRUN, that isn't already saved by VMSAVE (performed + * by common SVM code). */ - - /* XCR0 is restored on VMEXIT, save the current host value */ hostsa->xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK); - - /* PKRU is restored on VMEXIT, save the current host value */ hostsa->pkru = read_pkru(); - - /* MSR_IA32_XSS is restored on VMEXIT, save the currnet host value */ hostsa->xss = host_xss; }