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David Alan Gilbert" , , , Subject: Re: [PATCH v8 29/40] x86/compressed/64: add support for SEV-SNP CPUID table in #VC handlers Message-ID: <20220118142345.65wuub2p3alavhpb@amd.com> References: <20211210154332.11526-1-brijesh.singh@amd.com> <20211210154332.11526-30-brijesh.singh@amd.com> <20220113163913.phpu4klrmrnedgic@amd.com> <20220118043521.exgma53qrzrbalpd@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 15d5387d-b403-4f58-928d-08d9da8e2e95 X-MS-TrafficTypeDiagnostic: MN2PR12MB4093:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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:(4636009)(46966006)(36840700001)(40470700002)(26005)(186003)(70206006)(44832011)(7406005)(7416002)(966005)(81166007)(6916009)(70586007)(2616005)(336012)(508600001)(86362001)(45080400002)(83380400001)(4326008)(8676002)(16526019)(426003)(5660300002)(8936002)(40460700001)(6666004)(1076003)(36756003)(36860700001)(356005)(47076005)(82310400004)(2906002)(316002)(54906003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2022 14:24:05.0932 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 15d5387d-b403-4f58-928d-08d9da8e2e95 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: BN8NAM11FT021.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4093 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Jan 18, 2022 at 03:02:48PM +0100, Borislav Petkov wrote: > On Mon, Jan 17, 2022 at 10:35:21PM -0600, Michael Roth wrote: > > Unfortunately, in sev_enable(), between the point where snp_init() is > > called, and sev_status is actually set, there are a number of cpuid > > intructions which will make use of do_vc_no_ghcb() prior to sev_status > > being set (and it needs to happen in that order to set sev_status > > appropriately). After that point, snp_cpuid_active() would no longer be > > necessary, but during that span some indicator is needed in case this > > is just an SEV-ES guest trigger cpuid #VCs. > > You mean testing what snp_cpuid_info_create() set up is not enough? > > diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c > index 7bc7e297f88c..17cfe804bad3 100644 > --- a/arch/x86/kernel/sev-shared.c > +++ b/arch/x86/kernel/sev-shared.c > @@ -523,7 +523,9 @@ static int snp_cpuid_postprocess(u32 func, u32 subfunc, u32 *eax, u32 *ebx, > static int snp_cpuid(u32 func, u32 subfunc, u32 *eax, u32 *ebx, u32 *ecx, > u32 *edx) > { > - if (!snp_cpuid_active()) > + const struct snp_cpuid_info *c = snp_cpuid_info_get_ptr(); > + > + if (!c->count) > return -EOPNOTSUPP; > > if (!snp_cpuid_find_validated_func(func, subfunc, eax, ebx, ecx, edx)) { snp_cpuid_info_get_ptr() will always return non-NULL, since it's a pointer to the local copy of the cpuid page. But I can probably re-work it slightly that so snp_cpuid_info_get_ptr() does the same check that snp_cpuid_active() does, and have it return NULL if the copy hasn't been initialized, if that seems preferable to the separate snp_cpuid_active() function. > > --- > > Btw, all those > > /* SEV-SNP CPUID table should be set up now. */ > if (!snp_cpuid_active()) > sev_es_terminate(1, GHCB_TERM_CPUID); > > after snp_cpuid_info_create() has returned are useless either. If that > function returns, you know you're good to go wrt SNP. It seemed like a good thing to assert in case something slipped in later that tried to use snp_cpuid() without the table being initialized, but if I implement things the way you suggested above, snp_cpuid_info_get_ptr() will return NULL in that case, so we get that assurance for free. That does sound cleaner. > > Thx. > > -- > Regards/Gruss, > Boris. > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpeople.kernel.org%2Ftglx%2Fnotes-about-netiquette&data=04%7C01%7Cmichael.roth%40amd.com%7Cb8be348c4db84954006708d9da8b3820%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637781113782595576%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=HszNjYntQNNI827LNK4H8Tpx0vhpICo7y3FCzIvhNtc%3D&reserved=0