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Tue, 22 Nov 2022 18:22:47 +0000 Received: from BYAPR21MB1688.namprd21.prod.outlook.com ([fe80::1e50:78ec:6954:d6dd]) by BYAPR21MB1688.namprd21.prod.outlook.com ([fe80::1e50:78ec:6954:d6dd%4]) with mapi id 15.20.5880.002; Tue, 22 Nov 2022 18:22:47 +0000 From: "Michael Kelley (LINUX)" To: Borislav Petkov CC: "hpa@zytor.com" , KY Srinivasan , Haiyang Zhang , "wei.liu@kernel.org" , Dexuan Cui , "luto@kernel.org" , "peterz@infradead.org" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" , "lpieralisi@kernel.org" , "robh@kernel.org" , "kw@linux.com" , "bhelgaas@google.com" , "arnd@arndb.de" , "hch@infradead.org" , "m.szyprowski@samsung.com" , "robin.murphy@arm.com" , "thomas.lendacky@amd.com" , "brijesh.singh@amd.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "dave.hansen@linux.intel.com" , Tianyu Lan , "kirill.shutemov@linux.intel.com" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "ak@linux.intel.com" , "isaku.yamahata@intel.com" , "Williams, Dan J" , "jane.chu@oracle.com" , "seanjc@google.com" , "tony.luck@intel.com" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-arch@vger.kernel.org" , "iommu@lists.linux.dev" Subject: RE: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms Thread-Topic: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms Thread-Index: AQHY+es2O4adbWIH8UyWtCwRyUnUyq5JgOOAgAHDpcA= Date: Tue, 22 Nov 2022 18:22:46 +0000 Message-ID: References: <1668624097-14884-1-git-send-email-mikelley@microsoft.com> <1668624097-14884-8-git-send-email-mikelley@microsoft.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=eb4fe2b8-7043-4cc6-88fd-5a1cd8cde127;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Method=Standard;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=Internal;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2022-11-22T17:59:37Z;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BYAPR21MB1688.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: a2d72cfe-5ce3-49f8-ae00-08daccb68e52 X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Nov 2022 18:22:46.9775 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: bInvd3AFuRyPhamN1KmSYEB1mxnrLlBR4LDAEPYBT7eUZvFScHMNWZDs/SlJxTAyu3POiseqWsMNT3JBssW/iTo4+FqihXoGqxn//MdAcjk= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR21MB3361 X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO, RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_NONE 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 From: Borislav Petkov Sent: Monday, November 21, 2022 7:03 A= M >=20 > On Wed, Nov 16, 2022 at 10:41:30AM -0800, Michael Kelley wrote: > ... >=20 > > @@ -108,6 +115,7 @@ u64 cc_mkenc(u64 val) > > switch (vendor) { > > case CC_VENDOR_AMD: > > return val | cc_mask; > > + case CC_VENDOR_HYPERV: > > case CC_VENDOR_INTEL: > > return val & ~cc_mask; > > default: > > @@ -121,6 +129,7 @@ u64 cc_mkdec(u64 val) > > switch (vendor) { > > case CC_VENDOR_AMD: > > return val & ~cc_mask; > > + case CC_VENDOR_HYPERV: > > case CC_VENDOR_INTEL: > > return val | cc_mask; > > default: >=20 > Uuuh, this needs a BIG FAT COMMENT. >=20 > You're running on SNP and yet the enc/dec meaning is flipped. And that's > because of vTOM. >=20 > What happens if you have other types of SNP-based VMs on HyperV? The > isolation VMs thing? Or is that the same? >=20 > What happens when you do TDX guests with HyperV? >=20 > This becomes wrong then. >=20 > I think you need a more finer-grained check here in the sense of "is it > a HyperV guest using a paravisor and vTOM is enabled" or so. >=20 > Otherwise, I like the removal of the HyperV-specific checks ofc. >=20 I think the core problem here is the naming and meaning of CC_VENDOR_HYPERV. The name was created originally when the Hyper-V vTOM handling code was a lot of special cases. With the changes in this patch series that make the vTOM functionality more mainstream, the name would be better as CC_VENDOR_AMD_VTOM. vTOM is part of the AMD SEV-SNP spec, and it's a different way of doing the encryption from the "C-bit" based approach. As much as possible, I'm trying to not make it be Hyper-V specific, though currently we have N=3D1 for hypervisors that offer the vTOM option, so it's a little hard to generalize. With the thinking oriented that way, a Linux guest on Hyper-V using TDX will run with CC_VENDOR_INTEL. A Linux guest on Hyper-V that is fully enlightened to use the "C-bit" will run with CC_VENDOR_AMD. Dexuan Cui just posted a patch set for initial TDX support on Hyper-V, and I think that runs with CC_VENDOR_INTEL (Dexuan -- correct me if I'm wrong about that -- I haven't reviewed your patches yet). Tianyu Lan has a patch set out for Hyper-V guests using the "C-bit". That patch set still uses CC_VENDOR_HYPERV. Tianyu and I need to work through whether his patch set can run with CC_VENDOR_AMD like everyone else using the "C-bit" approach. Yes, the polarity of the AMD vTOM bit matches the polarity of the TDX GPA.SHARED bit, and is the opposite polarity of the AMD "C-bit". I'll add a comment to that effect. Anyway, that's where I think this should go. Does it make sense? Other thoughts? Michael