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Wed, 22 Jan 2025 04:30:14 +0000 Message-ID: <95a14f7d-4782-40b3-a55d-7cf67b911bbe@amd.com> Date: Wed, 22 Jan 2025 15:30:05 +1100 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH 2/7] guest_memfd: Introduce an object to manage the guest-memfd with RamDiscardManager Content-Language: en-US To: Peter Xu , Xu Yilun Cc: Chenyi Qiang , David Hildenbrand , Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Michael Roth , qemu-devel@nongnu.org, kvm@vger.kernel.org, Williams Dan J , Peng Chao P , Gao Chao , Xu Yilun References: <58b96b74-bf9c-45d3-8c2e-459ec2206fc8@intel.com> <8c8e024d-03dc-4201-8038-9e9e60467fad@amd.com> <4d22d3ce-a5a1-49f2-a578-8e0fe7d26893@amd.com> <2b799426-deaa-4644-aa17-6ef31899113b@intel.com> <2400268e-d26a-4933-80df-cfe44b38ae40@amd.com> <590432e1-4a26-4ae8-822f-ccfbac352e6b@intel.com> <2b2730f3-6e1a-4def-b126-078cf6249759@amd.com> From: Alexey Kardashevskiy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MEAPR01CA0057.ausprd01.prod.outlook.com (2603:10c6:201:30::21) To CH3PR12MB9194.namprd12.prod.outlook.com (2603:10b6:610:19f::7) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB9194:EE_|MW3PR12MB4347:EE_ X-MS-Office365-Filtering-Correlation-Id: bbc47d8d-e10d-4fe7-d501-08dd3a9d7701 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|366016; 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envelope-from=Alexey.Kardashevskiy@amd.com; helo=NAM12-BN8-obe.outbound.protection.outlook.com X-Spam_score_int: -51 X-Spam_score: -5.2 X-Spam_bar: ----- X-Spam_report: (-5.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.996, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.086, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 22/1/25 02:18, Peter Xu wrote: > On Tue, Jun 25, 2024 at 12:31:13AM +0800, Xu Yilun wrote: >> On Mon, Jan 20, 2025 at 03:46:15PM -0500, Peter Xu wrote: >>> On Mon, Jan 20, 2025 at 09:22:50PM +1100, Alexey Kardashevskiy wrote: >>>>> It is still uncertain how to implement the private MMIO. Our assumption >>>>> is the private MMIO would also create a memory region with >>>>> guest_memfd-like backend. Its mr->ram is true and should be managed by >>>>> RamdDiscardManager which can skip doing DMA_MAP in VFIO's region_add >>>>> listener. >>>> >>>> My current working approach is to leave it as is in QEMU and VFIO. >>> >>> Agreed. Setting ram=true to even private MMIO sounds hackish, at least >> >> The private MMIO refers to assigned MMIO, not emulated MMIO. IIUC, >> normal assigned MMIO is always set ram=true, >> >> void memory_region_init_ram_device_ptr(MemoryRegion *mr, >> Object *owner, >> const char *name, >> uint64_t size, >> void *ptr) >> { >> memory_region_init(mr, owner, name, size); >> mr->ram = true; >> >> >> So I don't think ram=true is a problem here. > > I see. If there's always a host pointer then it looks valid. So it means > the device private MMIOs are always mappable since the start? Yes. VFIO owns the mapping and does not treat shared/private MMIO any different at the moment. Thanks, > > Thanks, > -- Alexey