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Mon, 3 Aug 2020 03:00:16 +0000 Subject: Re: [RFC PATCH 0/8] KVM: x86/mmu: Introduce pinned SPTEs framework To: Sean Christopherson , Paolo Bonzini Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, eric van tassell , Tom Lendacky References: <20200731212323.21746-1-sean.j.christopherson@intel.com> From: Eric van Tassell Message-ID: Date: Sun, 2 Aug 2020 22:00:13 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 In-Reply-To: <20200731212323.21746-1-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DM6PR02CA0037.namprd02.prod.outlook.com (2603:10b6:5:177::14) To DM5PR12MB1307.namprd12.prod.outlook.com (2603:10b6:3:79::21) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.252.16.211] (165.204.77.11) by DM6PR02CA0037.namprd02.prod.outlook.com (2603:10b6:5:177::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3239.16 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1b2c9cd9-fb6e-48c8-b680-08d837595936 X-MS-Exchange-CrossTenant-AuthSource: DM5PR12MB1307.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Aug 2020 03:00:16.4838 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: EbeHsoPpmFtmJD57vAht7XKl/C4ALaUL3Hz/Q+JNfCKh50yXIbotD9SFXHhl7VGh7MJldiZANxTlhnAQzm6mSA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB2716 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Sean, What commit did you base your series on? Thanks. -evt(Eric van Tassell) On 7/31/20 4:23 PM, Sean Christopherson wrote: > SEV currently needs to pin guest memory as it doesn't support migrating > encrypted pages. Introduce a framework in KVM's MMU to support pinning > pages on demand without requiring additional memory allocations, and with > (somewhat hazy) line of sight toward supporting more advanced features for > encrypted guest memory, e.g. host page migration. > > The idea is to use a software available bit in the SPTE to track that a > page has been pinned. The decision to pin a page and the actual pinning > managment is handled by vendor code via kvm_x86_ops hooks. There are > intentionally two hooks (zap and unzap) introduced that are not needed for > SEV. I included them to again show how the flag (probably renamed?) could > be used for more than just pin/unpin. > > Bugs in the core implementation are pretty much guaranteed. The basic > concept has been tested, but in a fairly different incarnation. Most > notably, tagging PRESENT SPTEs as PINNED has not been tested, although > using the PINNED flag to track zapped (and known to be pinned) SPTEs has > been tested. I cobbled this variation together fairly quickly to get the > code out there for discussion. > > The last patch to pin SEV pages during sev_launch_update_data() is > incomplete; it's there to show how we might leverage MMU-based pinning to > support pinning pages before the guest is live. > > Sean Christopherson (8): > KVM: x86/mmu: Return old SPTE from mmu_spte_clear_track_bits() > KVM: x86/mmu: Use bits 2:0 to check for present SPTEs > KVM: x86/mmu: Refactor handling of not-present SPTEs in mmu_set_spte() > KVM: x86/mmu: Add infrastructure for pinning PFNs on demand > KVM: SVM: Use the KVM MMU SPTE pinning hooks to pin pages on demand > KVM: x86/mmu: Move 'pfn' variable to caller of direct_page_fault() > KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by SEV > KVM: SVM: Pin SEV pages in MMU during sev_launch_update_data() > > arch/x86/include/asm/kvm_host.h | 7 ++ > arch/x86/kvm/mmu.h | 3 + > arch/x86/kvm/mmu/mmu.c | 186 +++++++++++++++++++++++++------- > arch/x86/kvm/mmu/paging_tmpl.h | 3 +- > arch/x86/kvm/svm/sev.c | 141 +++++++++++++++++++++++- > arch/x86/kvm/svm/svm.c | 3 + > arch/x86/kvm/svm/svm.h | 3 + > 7 files changed, 302 insertions(+), 44 deletions(-) >