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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: 41c7b2dc-5dff-45dc-03fe-08dd34f11a48 X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Jan 2025 23:13:48.8751 (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: DlyLZDylJOXjUQVW+WP4SNZt+IE8NtKvRrFhmiFskr6s0JoJn68op/vSMCqhTG+nTAktvMyLVBHOk3QZEIdnhQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7537 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4F2D64000B X-Rspam-User: X-Stat-Signature: w5g571mqyeqitfzt1taoeb31ohqnssue X-HE-Tag: 1736896433-630821 X-HE-Meta: U2FsdGVkX1/7H63+Y1eO26dbtER2wOR4glW8vInTMKWZq7XCDDfPXr2/hzYxvKB83R2XO1+8VL926oNX1C35BA2aw+Qj35O1csJAdatsXK4Crm3gNHzKbXg073m06048DSqjoCXyK1CAS4uszcPCxOvqXayAeFmGWgtrMLRP2U4IGs619ORZ4l2canX2fVNaHa89ZPCA32UbbksdiMaifzIF9erbbR4+EPwq9qLsNV6DmDQbiD9++n7+HjIV5LGaCtGXftzuo7R+HOl3OidhMWw6D35Uoa4MrQebY5NkCuLFoGQ0ccnwFcqoegvpc/o/x3L5FXmwr7VTcEX9Q3kz0WwH4apKWyeirvTshTW7GLSDGRIkvq7qoLncWwKxC7KHNamGxdEHhUnd+47Eh19KMCbwMH86YjcMgpsMs+gLU2IIg+AAcftz8e6dw2iymVWOfmxKluCsk2oTsEbB0YAocj7SOh80jF9nwScTIjfKWawryg3/Z4e1imI2CrsXUrzIylgHsEjCbJylaEBojZLmX7fKYw3B+zkt4LU6EHhEW+0NaJInm5v1/K/27xNhr2czGjiXXyXvXRXwuShTUscy61JMz0NYSF83CM0fCoU9E97NYxyc92icqdD9WjY4UVG5xTBhyvFQkG3r20W9LhYSZui+ZLOzfrLCsnx/L7l0bQT5/VG0ycMgWhLCZpNo9uPA3j0s70FwwlHs6g1u/jAWz/7CBSyzpp0azjYzJzRMpLZGkug/qu9K7sTJyGmJ9DM9n2n5MuHGaMPOeZrs8FhEIR5rqbShf1i7v/+1SAep0zztBuIt/Rtuz2Le+vLSPmZNzwy72a3RLf5LH/TmGf0iidTTPnk8pXtvURwaXOgIKDnlWUeFCqQ8mw/UmHKCff/fhUjw9c4kcGe7vFu4IBokRvaMoMbj6I37ZxamAYV3qpSPLZFAiG6e6m9xQIzrQM4I6v4iQW+HmXMrUmaaciy MZrwwsBb y2SJhUMy4I26OsoLV0iFJcgxXl+DeoMvFUs1h4sp+MaZIKBzI/jHOm4+NaG0cGSWwSmfn5I9i7KaDLDbW/N34No/8HmAzo4ZHdWp2YbUnkC3erPYPHROJG1dV0il8zt2Y7n+yG4gDEcewQuY5cWfwTpIre17PU8iVjOOZOreUpmtO+mym1uij6KPVKRzAzXrv9zP9BT4l1bLKhCuwCnGZM/HCrTcPnYp8wYz0MjKk33s7yR2HrZcMyHVD0ppYfBhYatZ26XnIdMX/p1KQVxbPMpoHAIQIf6buTz4iTtSkfa6l1x/YreUz1UU5FKobFTtp6XTVDdiZtckszWJEiToTyPT9FpYIITKUp8o+JkOT07XAEe92xoQ12As4zUrdzJ963vsu2xpi7joKrPsqNNQK661QVGD87B5uXWatHO4xxWpI/Qyw1jfcqcqijjQCc41fqlByRBbDcIMADhE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks for the responses.=0A= =0A= > Do we really want another weirdly defined VMA flag? I'd really like to=0A= > avoid this.. =0A= =0A= I'd let Catalin chime in on this. My take of the reason for his suggestion = is=0A= that we want to reduce the affected configs to only the NVIDIA grace based= =0A= systems. The nvgrace-gpu module would be setting the flag and the=0A= new codepath will only be applicable there. Or am I missing something here?= =0A= =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 a= llow=0A= >>>>>> for mapping /dev/mem. Maybe one could just reject such cases (if KVM= PFN=0A= >>>>>> lookup code not already rejects them, which might just be that case = IIRC).=0A= >>>>>=0A= >>>>> At least VFIO enforces SHARED or it won't create the VMA.=0A= >>>>>=0A= >>>>> drivers/vfio/pci/vfio_pci_core.c: if ((vma->vm_flags & VM_SHARE= D) =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= >=0A= > I would check if it is a VM_PFNMAP, and outright refuse any page if=0A= > is_cow_mapping(vma->vm_flags) is true.=0A= =0A= So IIUC, I'll add the check to return -EINVAL for=0A= (vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)=0A= =0A= =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= >> Do we really want another weirdly defined VMA flag? I'd really like to= =0A= >> avoid this..=0A= >=0A= > Agreed.=0A= > =0A= > Can't we do a "this is a weird VM_PFNMAP thing, let's consult the VMA=0A= > prot + whatever PFN information to find out if it is weird-device and=0A= > how we could safely map it?"=0A= =0A= My understanding was that the new suggested flag VM_FORCE_CACHED=0A= was essentially to represent "whatever PFN information to find out if it is= =0A= weird-device". Is there an alternate reliable check to figure this out?=0A= =0A= =0A= > Ideally, we'd separate this logic from the "this is a normal VMA that=0A= > doesn't need any such special casing", and even stop playing PFN games=0A= > on these normal VMAs completely.=0A= =0A= Sorry David, it isn't clear to me what normal VMA mean here? I suppose you = mean=0A= the original KVM's non-nvgrace related code piece for MT_NORMAL memory?=0A= =0A= =0A= >> I assume MTE does not apply at all to VM_PFNMAP, at least=0A= >> arch_calc_vm_flag_bits() tells me that VM_MTE_ALLOWED should never get s= et=0A= >> there.=0A= >=0A= > As far as I know, it is completely platform specific what addresses MTE= =0A= > will work on. For instance, I would expect a MTE capable platform with=0A= > CXL to want to make MTE work on the CXL memory too.=0A= >=0A= > However, given we have no way of discovery, limiting MTE to boot time=0A= > system memory seems like the right thing to do for now - which we can=0A= > achieve by forbidding it from VM_PFNMAP.=0A= >=0A= > Having VFIO add VM_MTE_ALLOWED someday might make sense if someone=0A= > solves the discoverability problem.=0A= =0A= Currently in the patch we check the following. So Jason, is the suggestion = that=0A= we simply return error to forbid such condition if VM_PFNMAP is set?=0A= + else if (!mte_allowed && kvm_has_mte(kvm))=0A= =0A= - Ankit Agrawal=0A=