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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?kN9p2+BOqKTR3x8RQDyYRF8HEbfNxmmc3qex1vtF/RwEulHqVtnZtoC5WsnA?= =?us-ascii?Q?bZrhyBb2xrp6e/wLgrMr1ZbNCbcRRlGwxdaw7LbcSlMwBuI/u8VJbkzItsrw?= =?us-ascii?Q?Eh9CTAGyEEhJCm/T7Fqr92U2iGl32iqMUg4FxUcZHUEka5mS7skWYigwTuUi?= =?us-ascii?Q?ec7YcvKqrGQyedtZ/A6KkJ3v3vlyrnjdfE6c7joHJzQl0VSmpKqORHB1sq7M?= =?us-ascii?Q?45FtYOhXfRBmZnUpgq6hfTngjs7JuOr4kzbSHhvvNBJ97Jzhxr+8rGCz5WOj?= =?us-ascii?Q?gphTrtkzesUPtKGLXbVSJ535Gp6etB7lgUJqmKGm6I0NiED87BRQ16mzaG+1?= =?us-ascii?Q?/yMaNm6lqIi6NijO6G83ynwFKsuItxF1mar9Inai2GxzYGlxicSPEEuI9c3q?= =?us-ascii?Q?TzKFUSRZZE1rOEaxpbaXeNDtRLaujvuJLzM4s3MzVRcGy1RjsBb5PzkjItRc?= =?us-ascii?Q?UMheZgPn9tUG19BcLiJuijWAA8l8fQav06YlCfwvSUZsHyn1pPqdTTO1K+OR?= =?us-ascii?Q?BdbkC7FUrtIkYmFoeHldxry2kqWNBCzMRlYVRlwif/sS5qSaw1k7QxuALBw7?= =?us-ascii?Q?nsMNeKUYcyLqav8QmcTj34JqaxsEQFN0rAOSJ4twh+sJGyQJKt/R/O7KviuQ?= =?us-ascii?Q?4kyiYy00kgpoNZT4JHxO3zgwKCj9+MfsgLmFgZuXuYztgaEZyJ066CHutaWJ?= =?us-ascii?Q?p/2wfC+nbHrluwP969lD02IzrKULYNuRxcs8MdBHygoKee85HgvRzLk5gRHm?= =?us-ascii?Q?F9leqO1F27/UGfmHY9wRRL6ZN4pXZdqmHiwQ+MxKKkn9v6KjuYLfVWKrDSmd?= =?us-ascii?Q?GHp8ugioKoo3db+5x6w4CYp/i+ITpfLrTL3SX1Bae1yjB6krf6ZLhrbijbGp?= =?us-ascii?Q?gH0NhDJ8pnbEhA6UI9cR5NY5fbtBt5CUQD1nuec6rB0m0+4TA155MKTk3DUw?= =?us-ascii?Q?cHHeGbiaRsfkojf/iOEMF//khrEBTRURYvDAcoctbYdHUngbbwwmf2Pv83tN?= =?us-ascii?Q?7ZUkge1vELyTDsvx8B4oQr6ri7vTjSTf+43rflYQMrHz6YF/d1evuUBdaWSx?= =?us-ascii?Q?xSQCJwSf+F+WUaE3NksGbTWK1PHVUPqAZMf9/Vdj3jTujGpMHknpiZit8GLr?= =?us-ascii?Q?G0nxYC5NSDRwB4JGFT5RxvgDAdf1YdLOWAvgnQ+Q6syMJj6ts9LReCWEM621?= =?us-ascii?Q?TdA3/fq1sS5MWhPl2vyus1njjwXg9diwEDbx3J8kYMuI2Ggp7ROpNccjprTk?= =?us-ascii?Q?DUXgNFlcllqxZSh2VhtpQ7wPCeN7qUKh9+Yy1jlT+Tq/D9e93xR7KWifCvtA?= =?us-ascii?Q?Cj9g470lbZwwLRlBWWKHYefhqcKfXtZbT9cTEO3HT/jq9vhPcwEP+/RHoolP?= =?us-ascii?Q?bKknscKuldk3vYXC776VC8pQLR02ne5ASI4tS2NKzsl9RGKxVwtBTBqbo2En?= =?us-ascii?Q?wZV+21ENqaOWXjyf2LBVE4DdVPMePnI4s9/1GZ9iFy9KkkrPw2w68MZM0ypW?= =?us-ascii?Q?t7r74HiJ3H5lBqR5+HSLleI5klxM2g284kHsmgQXicpjKj+OeBz9ET4VbgBm?= =?us-ascii?Q?c5eYcbGlQ4QSLWfFfY4=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: a0cce8be-c0fe-420c-d37e-08dd2e727041 X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2025 16:52:00.3435 (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: utoTbf03w92k0ykoFxc6uTmVQoS80ezaDUGqyCOF6VUGOa4rWBxR+iv0kTxOhIF9 X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4184 On Fri, Dec 20, 2024 at 04:42:35PM +0100, David Hildenbrand wrote: > On 18.11.24 14:19, ankita@nvidia.com wrote: > > From: Ankit Agrawal > > > > Currently KVM determines if a VMA is pointing at IO memory by checking > > pfn_is_map_memory(). However, the MM already gives us a way to tell what > > kind of memory it is by inspecting the VMA. > > Do you primarily care about VM_PFNMAP/VM_MIXEDMAP VMAs, or also other VMA > types? I think this is exclusively about allowing cachable memory inside a VM_PFNMAP VMA (created by VFIO) remain cachable inside the guest VM. > > This patch solves the problems where it is possible for the kernel to > > have VMAs pointing at cachable memory without causing > > pfn_is_map_memory() to be true, eg DAX memremap cases and CXL/pre-CXL > > devices. This memory is now properly marked as cachable in KVM. > > Does this only imply in worse performance, or does this also affect > correctness? I suspect performance is the problem, correct? Correctness. Things like atomics don't work on non-cachable mappings. > Maybe one could just reject such cases (if KVM PFN lookup code not > already rejects them, which might just be that case IIRC). At least VFIO enforces SHARED or it won't create the VMA. drivers/vfio/pci/vfio_pci_core.c: if ((vma->vm_flags & VM_SHARED) == 0) This is pretty normal/essential for drivers.. Are you suggesting the VMA flags should be inspected more? VM_SHARED/PFNMAP before allowing this? Jason