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[2003:d8:2f06:a600:a397:de1d:2f8b:b66f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459e58542f3sm257349755e9.10.2025.08.11.08.33.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Aug 2025 08:33:57 -0700 (PDT) Message-ID: Date: Mon, 11 Aug 2025 17:33:54 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC V10 4/7] KVM: guest_memfd: Use guest mem inodes instead of anonymous inodes 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: <20250811090605.16057-2-shivankg@amd.com> <20250811090605.16057-10-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 11.08.25 11:06, Shivank Garg wrote: > From: Ackerley Tng > > guest_memfd's inode represents memory the guest_memfd is > providing. guest_memfd's file represents a struct kvm's view of that > memory. > > Using a custom inode allows customization of the inode teardown > process via callbacks. For example, ->evict_inode() allows > customization of the truncation process on file close, and > ->destroy_inode() and ->free_inode() allow customization of the inode > freeing process. > > Customizing the truncation process allows flexibility in management of > guest_memfd memory and customization of the inode freeing process > allows proper cleanup of memory metadata stored on the inode. > > Memory metadata is more appropriately stored on the inode (as opposed > to the file), since the metadata is for the memory and is not unique > to a specific binding and struct kvm. > > Co-developed-by: Fuad Tabba > Signed-off-by: Fuad Tabba > Signed-off-by: Ackerley Tng > Signed-off-by: Shivank Garg > --- [...] > > static int kvm_gmem_migrate_folio(struct address_space *mapping, > @@ -463,11 +503,71 @@ bool __weak kvm_arch_supports_gmem_mmap(struct kvm *kvm) > return true; > } > > +static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, > + loff_t size, u64 flags) > +{ > + struct inode *inode; > + > + inode = anon_inode_make_secure_inode(kvm_gmem_mnt->mnt_sb, name, NULL); > + if (IS_ERR(inode)) > + return inode; > + > + inode->i_private = (void *)(unsigned long)flags; > + inode->i_op = &kvm_gmem_iops; > + inode->i_mapping->a_ops = &kvm_gmem_aops; > + inode->i_mode |= S_IFREG; > + inode->i_size = size; > + mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); > + mapping_set_inaccessible(inode->i_mapping); > + /* Unmovable mappings are supposed to be marked unevictable as well. */ > + WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); > + > + return inode; > +} > + > +static struct file *kvm_gmem_inode_create_getfile(void *priv, loff_t size, > + u64 flags) > +{ > + static const char *name = "[kvm-gmem]"; > + struct inode *inode; > + struct file *file; > + int err; > + > + err = -ENOENT; Maybe add a comment here when the module reference will get dropped. And maybe we should just switch to fops_get() + fops_put? /* __fput() will take care of fops_put(). */ if (!fops_get(&kvm_gmem_fops)) goto err; > + > + inode = kvm_gmem_inode_make_secure_inode(name, size, flags); > + if (IS_ERR(inode)) { > + err = PTR_ERR(inode); > + goto err_put_module; > + } > + > + file = alloc_file_pseudo(inode, kvm_gmem_mnt, name, O_RDWR, > + &kvm_gmem_fops); > + if (IS_ERR(file)) { > + err = PTR_ERR(file); > + goto err_put_inode; > + } > + > + file->f_flags |= O_LARGEFILE; > + file->private_data = priv; > + > +out: > + return file; > + > +err_put_inode: > + iput(inode); > +err_put_module: > + module_put(kvm_gmem_fops.owner); fops_put(&kvm_gmem_fops); ? Acked-by: David Hildenbrand -- Cheers, David / dhildenb