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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: 96ec3086-c664-4a7c-24c6-08dd31bbf734 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Jan 2025 21:15:53.1973 (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: 9LCpjPbwljMkvarmOw2u76xxl4jWke8K0qcdCL+hRLBiBrJV6uBGrL2D2Zj8bv1d9aBpmPG/eOQB3f1hYkfXfg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB7927 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 048C040015 X-Rspam-User: X-Stat-Signature: 68qjrxnq8zwr5ciwjdokum3qdsr9hdau X-HE-Tag: 1736543757-276512 X-HE-Meta: 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 YzlmhCaM gAYNCNadkPmiRP70AnuiA5WoQFRI1WumFbSxpl5UAgbaD1a/EPMnIjXBeRaiDJjlm7b8isM8Xg9L5I4TBDsNqWjtfIoA96BYYBEOg0RJgB/X7MKP4PrSjBhGnzW8FquUO2yXzLGmpxjCmtiIANzF7MHhT7LAybU5GgM8OMRsluVoU61GNGjrWyuOdRIiiFk3fYKlRUiw14mGOzcj5CRPsSP4PCAX4/NKfCU9g9UZv8ucsxAJiKLK+SkJq1CAc2zgDzJT9ozOkJh3uI0tML8KFWNfsjVLJOPT5cqsjBdvF17i9oApSOM9mP3HHKk+lQMGMXGxJPtvowvgKhGcRDyE2qD5yPzeVyF3xSV0HkSowXvwwzbUEbhbO5W39fZC6J2x4i8ToZnfRINR5Ux2rusW7v8Ei1HlA1vrVp1/DAHc0nJ5CWp5/kwVmCmbIaYUEuNi2MVU3NpwigRa6TOQ= 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: >>>> This patch solves the problems where it is possible for the kernel to= =0A= >>>> have VMAs pointing at cachable memory without causing=0A= >>>> pfn_is_map_memory() to be true, eg DAX memremap cases and CXL/pre-CXL= =0A= >>>> devices. This memory is now properly marked as cachable in KVM.=0A= >>>=0A= >>> Does this only imply in worse performance, or does this also affect=0A= >>> correctness? I suspect performance is the problem, correct?=0A= >>=0A= >> Correctness. Things like atomics don't work on non-cachable mappings.=0A= >=0A= > Hah! This needs to be highlighted in the patch description. And maybe=0A= > this even implies Fixes: etc?=0A= =0A= Understood. I'll put that in the patch description.=0A= =0A= >>> Likely you assume to never end up with COW VM_PFNMAP -- I think it's=0A= >>> possible when doing a MAP_PRIVATE /dev/mem mapping on systems that allo= w=0A= >>> for mapping /dev/mem. Maybe one could just reject such cases (if KVM PF= N=0A= >>> lookup code not already rejects them, which might just be that case IIR= C).=0A= >>=0A= >> At least VFIO enforces SHARED or it won't create the VMA.=0A= >>=0A= >> drivers/vfio/pci/vfio_pci_core.c:=A0=A0=A0=A0=A0=A0 if ((vma->vm_flags &= VM_SHARED) =3D=3D 0)=0A= >=0A= > That makes a lot of sense for VFIO.=0A= =0A= So, I suppose we don't need to check this? Specially if we only extend the= =0A= changes to the following case:=0A= - type is VM_PFNMAP &&=0A= - user mapping is cacheable (MT_NORMAL or MT_NORMAL_TAGGED) &&=0A= - The suggested VM_FORCE_CACHED is set.=0A= =0A= - Ankit Agrawal=