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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: c0d51525-ed16-4999-e36f-08ddb94b7398 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Jul 2025 09:33:06.9045 (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: bS53zGTec7sVWMaIbRPKB4c9zpSRb/NwukWvEaOeDONX3GQJv14RghnawDwLqv/fq5zU+SoXv34xg2oeHlYRkA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ5PPFFA661D690 X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0C0231C000B X-Stat-Signature: ts5zk4q5f96cx3sytiep8ifct87gykor X-HE-Tag: 1751448790-275901 X-HE-Meta: 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 JxDgqPuB Uo0D8cUKppMRGdUVkQCM+iFaHEOSzZ5CkcMsDmA+WlzbwoAN60bnfpNRxe0zF1j684aZYfbm2jewVyC1ZDy2NkIPz/Dk5L8muRz4W5kUyj9yn2MygyW4xpcKbfweOQjYHro6m9mE3USXVauebIdPQ5de8I6DCERrb930yULszVvkMKZpKOv2RgkpYMSCzLYuiNmYDzTwBT5tEwpeTv3ssb4dRt9nLGrnPA2xIISsp5DZQaJ9k3tf7BKripjf+psHIwXkXPqwU+8agvq1lbnzZ2fS4hGv7qjBH2gjQ8wumyJfQmTnskg8XgaehVeR0H9T2LVGUQtLTc6YFjKZJsNg+/8IYcq0fJ/YIaFDGaFi1oQ/HWwNLdBqAdDnNwsYFpWQEyMOIRrB/UPH9MTk5rnxqnvr9V376evWVcZjVeAJ2FPXUMNQUTl4DAZZKIzuhbaTPthnAXE59nlbUZJR2OEUOQ92YDg/O26+z6bJbAef+o6JFm30= 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= Humble reminder for review.=