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[2003:d8:2f28:de00:1efe:3ea4:63ba:1713]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4563b73fa43sm131117765e9.21.2025.07.22.07.40.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jul 2025 07:40:34 -0700 (PDT) Message-ID: Date: Tue, 22 Jul 2025 16:40:31 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V9 0/7] Add NUMA mempolicy support for KVM guest-memfd 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> 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: > This series introduces NUMA-aware memory placement support for KVM guests > with guest_memfd memory backends. It builds upon Fuad Tabba's work that > enabled host-mapping for guest_memfd memory [1]. > > == Background == > KVM's guest-memfd memory backend currently lacks support for NUMA policy > enforcement, causing guest memory allocations to be distributed across host > nodes according to kernel's default behavior, irrespective of any policy > specified by the VMM. This limitation arises because conventional userspace > NUMA control mechanisms like mbind(2) don't work since the memory isn't > directly mapped to userspace when allocations occur. > Fuad's work [1] provides the necessary mmap capability, and this series > leverages it to enable mbind(2). > > == Implementation == > > This series implements proper NUMA policy support for guest-memfd by: > > 1. Adding mempolicy-aware allocation APIs to the filemap layer. > 2. Introducing custom inodes (via a dedicated slab-allocated inode cache, > kvm_gmem_inode_info) to store NUMA policy and metadata for guest memory. > 3. Implementing get/set_policy vm_ops in guest_memfd to support NUMA > policy. > > With these changes, VMMs can now control guest memory placement by mapping > guest_memfd file descriptor and using mbind(2) to specify: > - Policy modes: default, bind, interleave, or preferred > - Host NUMA nodes: List of target nodes for memory allocation > > These Policies affect only future allocations and do 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 (Not > supported for guest_memfd as it is unmovable by design). > > == Upstream Plan == > Phased approach as per David's guest_memfd extension overview [2] and > community calls [3]: > > Phase 1 (this series): > 1. Focuses on shared guest_memfd support (non-CoCo VMs). > 2. Builds on Fuad's host-mapping work. Just to clarify: this is based on Fuad's stage 1 and should probably still be tagged "RFC" until stage-1 is finally upstream. (I was hoping stage-1 would go upstream in 6.17, but I am not sure yet if that is still feasible looking at the never-ending review) I'm surprised to see that commit cbe4134ea4bc493239786220bd69cb8a13493190 Author: Shivank Garg Date: Fri Jun 20 07:03:30 2025 +0000 fs: export anon_inode_make_secure_inode() and fix secretmem LSM bypass was merged with the kvm export EXPORT_SYMBOL_GPL_FOR_MODULES(anon_inode_make_secure_inode, "kvm"); I thought I commented that this is something to done separately and not really "fix" material. Anyhow, good for this series, no need to touch that. -- Cheers, David / dhildenb