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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: 1696734e-ec93-4c8f-79fc-08ddb7795ce4 X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Jun 2025 01:56:43.3620 (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: 8jgqDHQOUQRY8rTNFhpu+hBRpJYdTEhnuD4VxXwB8kbxtYyc4ozj/ufTncxxHENI90RpBvaES7S/62UtZyIurA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL4PR12MB9479 X-Stat-Signature: cfe6d5hazs3toup6m93de9n5m9qjdbq1 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: EE892100002 X-Rspam-User: X-HE-Tag: 1751248613-912965 X-HE-Meta: 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 AIFrOyBG 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 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: > Sorry for the drive-by comment, but I was looking at this old series from= =0A= > Paolo (look at the cover letter and patch 5):=0A= >=0A= > https://lore.kernel.org/r/20250109133817.314401-1-pbonzini@redhat.com=0A= >=0A= > in which he points out that the arm64 get_vma_page_shift() function=0A= > incorrectly assumes that a VM_PFNMAP VMA is physically contiguous, which= =0A= > may not be the case if a driver calls remap_pfn_range() to mess around=0A= > with mappings within the VMA. I think that implies that the optimisation= =0A= > in 2aa53d68cee6 ("KVM: arm64: Try stage2 block mapping for host device=0A= > MMIO") is unsound.=0A= =0A= Hm yeah, that does seem problematic. Perhaps we need a new=0A= vma flag that could help the driver communicate to the KVM that the=0A= mapping is contiguous and it can go ahead with the optimization?=0A= E.g. something similar to VM_ALLOW_ANY_UNCACHED.=0A= =0A= > But it got me thinking -- given that remap_pfn_range() also takes a 'prot= '=0A= > argument, how do we ensure that this is reflected in the guest? It feels= =0A= > a bit dodgy to rely on drivers always passing 'vma->vm_page_prot'.=0A= >=0A= > Will=0A= =0A= The driver use the vm_page_prot sent through the VMM VMA and may=0A= update some flags. Is your question that if we can trust the driver doing= =0A= the right thing and properly map through remap_pfn_range so as to not=0A= conflict with VMM (vma->vm_page_prot)?=0A=