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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: c4f1b4d6-4b0a-4c89-87d9-08ddbb1b0387 X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Jul 2025 16:51:25.4127 (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: AsQPB7IdONxizx+7MV/Ia2PnirwkQwAY8bFeZo4Lq2PEJjurNOPwoqgs4jnAazP8UHIe0eFjBBC6/UlN6nDXNg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8891 X-Stat-Signature: kuebr9hh74wc5ux3337p1pie71bc5fz9 X-Rspamd-Queue-Id: CCA73A0003 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1751647888-408481 X-HE-Meta: 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 ITpgA49R 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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: Thank you Jason and David to review this and other patches in the series!= =0A= Comments inline.=0A= =0A= >>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 * COW VM_PFNMAP is possible when = doing a MAP_PRIVATE=0A= >>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 * /dev/mem mapping on systems tha= t allow such mapping.=0A= >>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 * Reject such case.=0A= >>>=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 */=0A= >>> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 s2_force_noncacheable =3D true;=0A= >>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 if (is_cow_mapping(vm_flags))=0A= >>> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 return -EINV= AL;=0A= >>=0A= >> I still would like an explanation why we need to block this.=0A= >>=0A= >> COW PFNMAP is like MIXEDMAP, you end up with a VMA where there is a=0A= >> mixture of MMIO and normal pages. Arguably you are supposed to use=0A= >> vm_normal_page() not pfn_is_map_memory(), but that seems difficult for= =0A= >> KVM.=0A= >>=0A= >> Given we exclude the cachable case with the pfn_is_map_memory() we=0A= >> know this is the non-struct page memory already, so why do we need to=0A= >> block the COW?=0A= >>=0A= >> I think the basic rule we are going for is that within the VMA the=0A= >> non-normal/special PTE have to follow the vma->vm_pgprot while the=0A= >> normal pages have to be cachable.=0A= >>=0A= >> So if we find a normal page (ie pfn_is_map_memory()) then we know it=0A= >> is cachable and s2_force_noncacheable =3D false. Otherwise we use the=0A= >> vm_pgprot to decide if the special PTE is cachable.=0A= >>=0A= >> David can you think of any reason to have this is_cow_mapping() test?=0A= >=0A= > I think with that reasoning, it should be fine to drop it.=0A= >=0A= > I think, the COW test made sense when we were talking about limiting it= =0A= > to VM_PFNMAP only and simplifying by dropping other checks. Then, it=0A= > would have identified that something is certainly not "normal" memory.=0A= >=0A= =0A= Ack, I'll drop the check in the next version.=0A= =0A= > Then this logic that immediately follows:=0A= >=0A= > if (is_vma_cacheable && s2_force_noncacheable)=0A= > return -EINVAL;=0A= >=0A= > Doesn't make alot of sense either, the only cases that set=0A= > s2_force_noncacheable=3Dtrue are the else block of 'if (is_vma_cacheable)= '=0A= > so this is dead code too.=0A= =0A= I had left it there so that that condition doesn't get violated in the=0A= future. But perhaps it doesn't make much sense to keep it. I'll remove in= =0A= the next version.=0A= =0A= > Seems like this still needs some cleanup to remove these impossible=0A= > conditions. The logic make sense to me otherwise though.=0A= =0A= Sure, I'll fix that in the next version.=0A= =0A=