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[2003:d8:2f28:de00:1efe:3ea4:63ba:1713]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4563b73f76esm131398455e9.18.2025.07.22.08.24.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jul 2025 08:24:09 -0700 (PDT) Message-ID: Date: Tue, 22 Jul 2025 17:24:06 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V9 6/7] KVM: guest_memfd: Enforce NUMA mempolicy using shared policy To: Shivank Garg , seanjc@google.com, vbabka@suse.cz, willy@infradead.org, akpm@linux-foundation.org, shuah@kernel.org, pbonzini@redhat.com, brauner@kernel.org, viro@zeniv.linux.org.uk Cc: ackerleytng@google.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, pvorel@suse.cz, bfoster@redhat.com, tabba@google.com, vannapurve@google.com, chao.gao@intel.com, bharata@amd.com, nikunj@amd.com, michael.day@amd.com, shdhiman@amd.com, yan.y.zhao@intel.com, Neeraj.Upadhyay@amd.com, thomas.lendacky@amd.com, michael.roth@amd.com, aik@amd.com, jgg@nvidia.com, kalyazin@amazon.com, peterx@redhat.com, jack@suse.cz, rppt@kernel.org, hch@infradead.org, cgzones@googlemail.com, ira.weiny@intel.com, rientjes@google.com, roypat@amazon.co.uk, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, kent.overstreet@linux.dev, ying.huang@linux.alibaba.com, apopple@nvidia.com, chao.p.peng@intel.com, amit@infradead.org, ddutile@redhat.com, dan.j.williams@intel.com, ashish.kalra@amd.com, gshan@redhat.com, jgowans@amazon.com, pankaj.gupta@amd.com, papaluri@amd.com, yuzhao@google.com, suzuki.poulose@arm.com, quic_eberman@quicinc.com, aneeshkumar.kizhakeveetil@arm.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-coco@lists.linux.dev References: <20250713174339.13981-2-shivankg@amd.com> <20250713174339.13981-9-shivankg@amd.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 13.07.25 19:43, Shivank Garg wrote: > Previously, guest-memfd allocations followed local NUMA node id in absence > of process mempolicy, resulting in arbitrary memory allocation. > Moreover, mbind() couldn't be used by the VMM as guest memory wasn't > mapped into userspace when allocation occurred. > > Enable NUMA policy support by implementing vm_ops for guest-memfd mmap > operation. This allows the VMM to map the memory and use mbind() to set the > desired NUMA policy. The policy is stored in the inode structure via > kvm_gmem_inode_info, as memory policy is a property of the memory (struct > inode) itself. The policy is then retrieved via mpol_shared_policy_lookup() > and passed to filemap_grab_folio_mpol() to ensure that allocations follow > the specified memory policy. > > This enables the VMM to control guest memory NUMA placement by calling > mbind() on the mapped memory regions, providing fine-grained control over > guest memory allocation across NUMA nodes. > > The policy change only affect future allocations and does not migrate > existing memory. This matches mbind(2)'s default behavior which affects > only new allocations unless overridden with MPOL_MF_MOVE/MPOL_MF_MOVE_ALL > flags, which are not supported for guest_memfd as it is unmovable. > > Suggested-by: David Hildenbrand > Signed-off-by: Shivank Garg > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb