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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA1PR12MB7199.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 125ff6e2-ff33-4593-f5c3-08ddb537eb3e X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Jun 2025 05:03:13.0584 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: UHY5HVdGRMC1jgQcAeT3EOEBXaHmnaoSXx9xQ05r+pFgNishBt9nA0e7uz9JPhvaTbiBcZuT9CzDedVpimRLRA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB8082 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E7D3514000A X-Stat-Signature: ttgmiy4hkgquznpb8oar4yf995h8tajq X-Rspam-User: X-HE-Tag: 1751000599-118213 X-HE-Meta: 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 oe4GyvFX uEr1JnUPO0p/T09UiBcoRkQx5io28MHXObyAHwJef5YXQdkfjynAH7svvL927hPXNtW5wiQmCwJkpvA8sQqAD72cBxObzyujnHDulz4L3RdT+XIriCkVQL+95EqQlgkLLB9ZayI3wV8cV4KAwOcW3Nj7Lh2JKZV4EM+5uA0tZy1plLzg9SQiRyEzyoao81n92jNbn4YTVngIY4l4WlogkxZa9rXM7raJ3mwudDFAq+wwbn8ce8jFsSspGe7bxaOh81s1pD0mcr8u1zfuAb93qE+B0/fy30kSZ0f/MmNOcBF/1zLThXpCnKSbQfS4rBt76oF+74SpBRxwz3pD3ao8iUyGQyoOENW2SkBhT6gLVNTfNSSvXPJ1qgkV+Gkb9sK2YXFOJi4x5ST+/O9qSUFb31PvpNWX1Nt/pEGuTpUucM+CUiIGQ1g3BPBWFKWoSbB53eyGI06Hj+qDy/Qc/kp2Rh09KB+wFdyETxTPm/WCGD2h5v00= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > Grace based platforms such as Grace Hopper/Blackwell Superchips have=0A= > CPU accessible cache coherent GPU memory. The GPU device memory is=0A= > essentially a DDR memory and retains properties such as cacheability,=0A= > unaligned accesses, atomics and handling of executable faults. This=0A= > requires the device memory to be mapped as NORMAL in stage-2.=0A= >=0A= > Today KVM forces the memory to either NORMAL or DEVICE_nGnRE depending=0A= > on whether the memory region is added to the kernel. The KVM code is=0A= > thus restrictive and prevents device memory that is not added to the=0A= > kernel to be marked as cacheable. The patch aims to solve this.=0A= >=0A= > A cachebility check is made by consulting the VMA pgprot value. If=0A= > the pgprot mapping type is cacheable, it is considered safe to be=0A= > mapped cacheable as the KVM S2 will have the same Normal memory type=0A= > as the VMA has in the S1 and KVM has no additional responsibility=0A= > for safety.=0A= >=0A= > Note when FWB (Force Write Back) is not enabled, the kernel expects to=0A= > trivially do cache management by flushing the memory by linearly=0A= > converting a kvm_pte to phys_addr to a KVA. The cache management thus=0A= > relies on memory being mapped. Since the GPU device memory is not kernel= =0A= > mapped, exit when the FWB is not supported. Similarly, ARM64_HAS_CACHE_DI= C=0A= > allows KVM to avoid flushing the icache and turns icache_inval_pou() into= =0A= > a NOP. So the cacheable PFNMAP is made contingent on these two hardware= =0A= > features.=0A= >=0A= > The ability to safely do the cacheable mapping of PFNMAP is exposed=0A= > through a KVM capability for userspace consumption.=0A= >=0A= > The changes are heavily influenced by the discussions among=0A= > maintainers Marc Zyngier and Oliver Upton besides Jason Gunthorpe,=0A= > Catalin Marinas, David Hildenbrand, Sean Christopherson [1]. Many=0A= > thanks for their valuable suggestions.=0A= >=0A= > Applied over next-20250610 and tested on the Grace Blackwell=0A= > platform by booting up VM, loading NVIDIA module [2] and running=0A= > nvidia-smi in the VM.=0A= >=0A= > To run CUDA workloads, there is a dependency on the IOMMUFD and the=0A= > Nested Page Table patches being worked on separately by Nicolin Chen.=0A= > (nicolinc@nvidia.com). NVIDIA has provided git repositories which=0A= > includes all the requisite kernel [3] and Qemu [4] patches in case=0A= > one wants to try.=0A= >=0A= > v8 -> v9=0A= > 1. Included MIXEDMAP to also be considered for cacheable mapping.=0A= > (Jason Gunthorpe).=0A= > 2. Minor text nits (Jason Gunthorpe).=0A= =0A= A humble reminder for the review.=