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Tue, 4 Mar 2025 10:52:40 +0000 Date: Tue, 4 Mar 2025 18:51:20 +0800 From: Yan Zhao To: Paolo Bonzini CC: , , , Subject: Re: [PATCH v3 5/6] KVM: x86: remove shadow_memtype_mask Message-ID: Reply-To: Yan Zhao References: <20250304060647.2903469-1-pbonzini@redhat.com> <20250304060647.2903469-6-pbonzini@redhat.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250304060647.2903469-6-pbonzini@redhat.com> X-ClientProxiedBy: SG2PR02CA0013.apcprd02.prod.outlook.com (2603:1096:3:17::25) To DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::6) 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: DS7PR11MB5966:EE_|CH3PR11MB7940:EE_ X-MS-Office365-Filtering-Correlation-Id: eba4d7bb-1a08-4337-17c5-08dd5b0aaf68 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?+yFjLzVjENDhzYVzGOQqcgclbSYXFYvSajkaLbkIF55N0MLjfUMHqX70sKeC?= =?us-ascii?Q?z8s9t7jDLBlTZdBYaydevznreJ+XKQ/+JI+vwUBUG3zyOnYzxRYTQj2nG8/k?= =?us-ascii?Q?pLFjQId8+eD3UQ9NR883AuSRQjYCg8zVgaC4dN0jiW5sN0pDyWab2h1CbjKp?= =?us-ascii?Q?qqypLnBps5anRHpGkEgNdk3GW3pmyiEeoGNilvOeB9hfQJPU3F/0u7HoMzfS?= =?us-ascii?Q?ZlgRFs3OXbwBURe6DoUpNqtGplr67q3yIESC9YGQ/4aPLzRHKgOGWRaIVW4a?= =?us-ascii?Q?yB7JhrYaWGScN2egO+KENKck5pDDXqr0Th9+LzId+FIiskc2TfERoYJxtydI?= =?us-ascii?Q?r93P24TlNQOS9fl6UhoO5t69qo61dgIj68KdVI0Qd/ur4pcD2MLSAUyHDjkJ?= =?us-ascii?Q?xSN4ppNDivVz/JPKM32FxS1wlpvWT7M3aFfw6AjUQxWytqeYLEYxOjCFVHff?= =?us-ascii?Q?v+KEQAEOLBl6FtvEfLjHpLzbrQqmBRO02M3dDGjKqwqsPof2u1zyglmhEjcb?= =?us-ascii?Q?7zQ+QwLvEX4l3O2DYc0zeEcIOfjyl55OUW0TtdG1tdFDIshuwHTFcJ+Dodya?= =?us-ascii?Q?kD0ZZx7GI79+VJEj5aWJEvpiifsC7+tBdS+ZGbEhVHculrNfZi/fULMsnn//?= =?us-ascii?Q?CYNfryh9LsxxzOiBDdNAtqxMmHf6LwzC5rmteVGhW5/pZZg1PQNVY1OLmEVi?= =?us-ascii?Q?jiLJtWJKr93xyoCnCs5cIGz2WxY1Ffn3VrNK3E498Uh9in0TWCoLGVI6VF/x?= =?us-ascii?Q?2cDQ535p1uEVUf27RS9tHq4Qs1UYvKaNcyFcGOLXVXcQxh4aewHGRJuLKWbY?= =?us-ascii?Q?WLuj/vivsvty2SU2dTva8TXKBrj9/uqI+BeGsk622J79ZhgJoEeMiciMf2tA?= =?us-ascii?Q?Ifq+fyWlC1SVeYvcGu6Tfr6nwUOyqhb979I5JLqYVDsUnNA3vMhUDMG1His2?= =?us-ascii?Q?C+XhYCnstSYLe+LbDQ7ncGVIXOshSKxuxSMxIeRK4t46C0JnkX0fwGwBIg6P?= =?us-ascii?Q?oZLfbhzHRpCit5XiCutK08WMftdE/TGEnZ0YfvKxxFVrHZnUScxZ0ignTYjq?= =?us-ascii?Q?Hni5M+wZlzHZKAidrD2ZBa6rD8s3izs4dPyma1MX+ciFmieikCE5tmtkv6c0?= =?us-ascii?Q?ldBW2n2hgs7bJZ38B90q2vgr6ttnHnYoGPjp39pvvVdAQyeT2ZgbCkE9Epdh?= =?us-ascii?Q?VQiu4o5sTVZ/6Yl6qcZL0fXv8K9cHu1dK8gjdGXvCtGdHaQg68WlPnio3Qjc?= =?us-ascii?Q?8TVb+hn/qknYTGQmefCV/fGgf3wjdeAnbfDQObK2+vs2XH/RPNDQCAxY72GC?= =?us-ascii?Q?74BG0wkXjJ4ddXusB3ozInpdJNXSXKEUASo/gsMi96HPcn0voHeF4gRkZS/K?= =?us-ascii?Q?TWSYEDavu2zCBuFJ5Rf+F0BcNhWEhYMytV1hbaHLrogO5BZqDZSGFz19n4Rc?= =?us-ascii?Q?WBF3W6aHm9oIfk7OyH4NDbePQjT6Ad13jfnqvO7yJlCrDVxVtZlo9TbDo8VG?= =?us-ascii?Q?v6ZplQBrAI/ax4nW+dej8YNDX162INZLYwdnuUQ3FY9MvWkYnv3xHKQkMKj+?= =?us-ascii?Q?XQqRx2Di6PRGCX0n8zkRVXQK1FtwJrz4RSDJc/XN?= X-MS-Exchange-CrossTenant-Network-Message-Id: eba4d7bb-1a08-4337-17c5-08dd5b0aaf68 X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Mar 2025 10:52:40.8274 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 4jslR6SS0W48tPx/JbuJb2h0AGHFir3uLuAV0Vl+k1twEpaYVFM6SFj/Yar+HYDsWdlkWBE6bhFgrrTK6qO5+A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR11MB7940 X-OriginatorOrg: intel.com On Tue, Mar 04, 2025 at 01:06:46AM -0500, Paolo Bonzini wrote: > The IGNORE_GUEST_PAT quirk is inapplicable, and thus always-disabled, > if shadow_memtype_mask is zero. As long as vmx_get_mt_mask is not For shadow paging case, current KVM always ignores guest PAT, i.e., the quirk is always-enabled. However, this might be negligible, as non-coherent DMA is unlikely to function well with shadow paging anyway, if I don't miss anything. > called for the shadow paging case, there is no need to consult > shadow_memtype_mask and it can be removed altogether. ... > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 5b45fca3ddfa..8bf50cecc75c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -13544,8 +13544,10 @@ static void kvm_noncoherent_dma_assignment_start_or_stop(struct kvm *kvm) > * due to toggling the "ignore PAT" bit. Zap all SPTEs when the first > * (or last) non-coherent device is (un)registered to so that new SPTEs > * with the correct "ignore guest PAT" setting are created. > + * > + * If KVM always honors guest PAT, however, there is nothing to do. > */ > - if (kvm_mmu_may_ignore_guest_pat(kvm)) > + if (kvm_check_has_quirk(kvm, KVM_X86_QUIRK_IGNORE_GUEST_PAT)) > kvm_zap_gfn_range(kvm, gpa_to_gfn(0), gpa_to_gfn(~0ULL)); > } > > -- > 2.43.5 > >