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Thu, 20 Feb 2025 00:55:46 +0000 Date: Thu, 20 Feb 2025 08:55:36 +0800 From: Chao Gao To: Jon Kohler CC: Sean Christopherson , Paolo Bonzini , Eiichi Tsukata , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "vkuznets@redhat.com" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH] KVM: x86: hyper-v: Inhibit APICv with VP Assist on SPR/EMR Message-ID: References: <20240806053701.138337-1-eiichi.tsukata@nutanix.com> <028DBF5C-FB12-415C-B128-3EF275CF2A8C@nutanix.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <028DBF5C-FB12-415C-B128-3EF275CF2A8C@nutanix.com> X-ClientProxiedBy: SI2PR04CA0004.apcprd04.prod.outlook.com (2603:1096:4:197::22) To CH3PR11MB8660.namprd11.prod.outlook.com (2603:10b6:610:1ce::13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR11MB8660:EE_|IA1PR11MB6540:EE_ X-MS-Office365-Filtering-Correlation-Id: 1107ed2c-0e83-4cf4-01bb-08dd51494f96 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024; 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Therefore, >>> PV EOI should be basically a no-op with APICv in use. >> >> Per Chao, this is a ucode bug though. Speculating wildly, I wonder if Intel added >> acceleration and/or redirection of HV_X64_MSR_EOI when APICv is enabled, e.g. to >> speed up existing VMs, and something went sideways. > >Hey Sean, Chao, Paolo, quick follow up on this one. > >Eiichi was working on pulling down Intel Microcode 20250211 [1], and I had >asked to retest this one. > >Knock on wood, it looks like the issue is “gone” with 20250211 on SPR/EMR > >The EMR [2] and SPR [3] release notes allude to some Erratum regarding >some vmexit fixups that sound interesting, but I’m not sure if they are actually >the backing issue, Yes. EMR137 and SPR141 are exactly the backing issue and have been fixed in recent microcode releases. >or if this is sheer coincidence, or if there was another fix >but just isn’t fully documented as an errata? > >These two are listed as “fixed” in the release notes: >EMR137. VM Exit Following MOV to CR8 Instruction May Lead to Unexpected IDT Vectoring-Information >SPR141. VM Exit Following MOV to CR8 Instruction May Lead to Unexpected IDT Vectoring-Information > >@Chao - could you help confirm our observations one way or the other? > >[1] https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/releases/tag/microcode-20250211 >[2] https://cdrdv2.intel.com/v1/dl/getContent/793902 (EMR microcode release notes) >[3] https://cdrdv2.intel.com/v1/dl/getContent/772415 (SPR microcode release notes)