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AJvYcCW+xiotsvnbFdtlTicBIoqKGRyjAaND95PD6n9zGAWA6IooUHVyUj83gHZW9tGIYsuH+RwTADZ7DkR1xtRwEg0=@vger.kernel.org X-Gm-Message-State: AOJu0YxrTBuCuRr5TuwrNJAeV4j+AwlZ11zyMf/0nGUgehcdgJFqum69 JSL1x9EKjojfo/5QwvlfFEF3pcdBv2iRjiTsyIMnazblQg4cwFr/1qCS0YAUNgO/bNekipJgGdM RDbvMzLQylw== X-Google-Smtp-Source: AGHT+IGmB4tQYHflNeidIdzxEAiQVgVR06U6vmB3abdN612fldcUCZhwfNaA1J0qHtwaVn3gWHMxg6azF1vb X-Received: from pjbpv7.prod.google.com ([2002:a17:90b:3c87:b0:301:1ea9:63b0]) (user=afranji job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:5750:b0:30e:3737:7c71 with SMTP id 98e67ed59e1d1-30e7d57e4e6mr6123056a91.20.1747423191645; Fri, 16 May 2025 12:19:51 -0700 (PDT) Date: Fri, 16 May 2025 19:19:22 +0000 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.49.0.1101.gccaa498523-goog Message-ID: <754b4898c3362050071f6dd09deb24f3c92a41c3.1747368092.git.afranji@google.com> Subject: [RFC PATCH v2 02/13] KVM: guest_memfd: Make guest mem use guest mem inodes instead of anonymous inodes From: Ryan Afranji To: afranji@google.com, ackerleytng@google.com, pbonzini@redhat.com, seanjc@google.com, tglx@linutronix.de, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, tabba@google.com Cc: mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, shuah@kernel.org, andrew.jones@linux.dev, ricarkol@google.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, yu.c.zhang@linux.intel.com, vannapurve@google.com, erdemaktas@google.com, mail@maciej.szmigiero.name, vbabka@suse.cz, david@redhat.com, qperret@google.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, sagis@google.com, jthoughton@google.com From: Ackerley Tng Using guest mem inodes allows us to store metadata for the backing memory on the inode. Metadata will be added in a later patch to support HugeTLB pages. Metadata about backing memory should not be stored on the file, since the file represents a guest_memfd's binding with a struct kvm, and metadata about backing memory is not unique to a specific binding and struct kvm. Signed-off-by: Fuad Tabba Signed-off-by: Ackerley Tng --- include/uapi/linux/magic.h | 1 + virt/kvm/guest_memfd.c | 132 +++++++++++++++++++++++++++++++------ virt/kvm/kvm_main.c | 7 +- virt/kvm/kvm_mm.h | 9 ++- 4 files changed, 124 insertions(+), 25 deletions(-) diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h index bb575f3ab45e..169dba2a6920 100644 --- a/include/uapi/linux/magic.h +++ b/include/uapi/linux/magic.h @@ -103,5 +103,6 @@ #define DEVMEM_MAGIC 0x454d444d /* "DMEM" */ #define SECRETMEM_MAGIC 0x5345434d /* "SECM" */ #define PID_FS_MAGIC 0x50494446 /* "PIDF" */ +#define GUEST_MEMORY_MAGIC 0x474d454d /* "GMEM" */ #endif /* __LINUX_MAGIC_H__ */ diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index b2aa6bf24d3a..2ee26695dc31 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -1,12 +1,16 @@ // SPDX-License-Identifier: GPL-2.0 +#include #include #include #include +#include #include #include #include "kvm_mm.h" +static struct vfsmount *kvm_gmem_mnt; + struct kvm_gmem { struct kvm *kvm; struct xarray bindings; @@ -318,9 +322,51 @@ static struct file_operations kvm_gmem_fops = { .fallocate = kvm_gmem_fallocate, }; -void kvm_gmem_init(struct module *module) +static const struct super_operations kvm_gmem_super_operations = { + .statfs = simple_statfs, +}; + +static int kvm_gmem_init_fs_context(struct fs_context *fc) +{ + struct pseudo_fs_context *ctx; + + if (!init_pseudo(fc, GUEST_MEMORY_MAGIC)) + return -ENOMEM; + + ctx = fc->fs_private; + ctx->ops = &kvm_gmem_super_operations; + + return 0; +} + +static struct file_system_type kvm_gmem_fs = { + .name = "kvm_guest_memory", + .init_fs_context = kvm_gmem_init_fs_context, + .kill_sb = kill_anon_super, +}; + +static int kvm_gmem_init_mount(void) +{ + kvm_gmem_mnt = kern_mount(&kvm_gmem_fs); + + if (WARN_ON_ONCE(IS_ERR(kvm_gmem_mnt))) + return PTR_ERR(kvm_gmem_mnt); + + kvm_gmem_mnt->mnt_flags |= MNT_NOEXEC; + return 0; +} + +int kvm_gmem_init(struct module *module) { kvm_gmem_fops.owner = module; + + return kvm_gmem_init_mount(); +} + +void kvm_gmem_exit(void) +{ + kern_unmount(kvm_gmem_mnt); + kvm_gmem_mnt = NULL; } static int kvm_gmem_migrate_folio(struct address_space *mapping, @@ -402,11 +448,71 @@ static const struct inode_operations kvm_gmem_iops = { .setattr = kvm_gmem_setattr, }; +static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, + loff_t size, u64 flags) +{ + struct inode *inode; + + inode = alloc_anon_secure_inode(kvm_gmem_mnt->mnt_sb, name); + 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; + if (!try_module_get(kvm_gmem_fops.owner)) + 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); +err: + file = ERR_PTR(err); + goto out; +} + static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) { - const char *anon_name = "[kvm-gmem]"; struct kvm_gmem *gmem; - struct inode *inode; struct file *file; int fd, err; @@ -420,32 +526,16 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) goto err_fd; } - file = anon_inode_create_getfile(anon_name, &kvm_gmem_fops, gmem, - O_RDWR, NULL); + file = kvm_gmem_inode_create_getfile(gmem, size, flags); if (IS_ERR(file)) { err = PTR_ERR(file); goto err_gmem; } - file->f_flags |= O_LARGEFILE; - - inode = file->f_inode; - WARN_ON(file->f_mapping != inode->i_mapping); - - 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)); - kvm_get_kvm(kvm); gmem->kvm = kvm; xa_init(&gmem->bindings); - list_add(&gmem->entry, &inode->i_mapping->i_private_list); + list_add(&gmem->entry, &file_inode(file)->i_mapping->i_private_list); fd_install(fd, file); return fd; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 69782df3617f..1e3fd81868bc 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -6412,7 +6412,9 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) if (WARN_ON_ONCE(r)) goto err_vfio; - kvm_gmem_init(module); + r = kvm_gmem_init(module); + if (r) + goto err_gmem; r = kvm_init_virtualization(); if (r) @@ -6433,6 +6435,8 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module) err_register: kvm_uninit_virtualization(); err_virt: + kvm_gmem_exit(); +err_gmem: kvm_vfio_ops_exit(); err_vfio: kvm_async_pf_deinit(); @@ -6464,6 +6468,7 @@ void kvm_exit(void) for_each_possible_cpu(cpu) free_cpumask_var(per_cpu(cpu_kick_mask, cpu)); kmem_cache_destroy(kvm_vcpu_cache); + kvm_gmem_exit(); kvm_vfio_ops_exit(); kvm_async_pf_deinit(); kvm_irqfd_exit(); diff --git a/virt/kvm/kvm_mm.h b/virt/kvm/kvm_mm.h index acef3f5c582a..dcacb76b8f00 100644 --- a/virt/kvm/kvm_mm.h +++ b/virt/kvm/kvm_mm.h @@ -68,17 +68,20 @@ static inline void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, #endif /* HAVE_KVM_PFNCACHE */ #ifdef CONFIG_KVM_PRIVATE_MEM -void kvm_gmem_init(struct module *module); +int kvm_gmem_init(struct module *module); +void kvm_gmem_exit(void); int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args); int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset); void kvm_gmem_unbind(struct kvm_memory_slot *slot); #else -static inline void kvm_gmem_init(struct module *module) +static inline int kvm_gmem_init(struct module *module) { - + return 0; } +static inline void kvm_gmem_exit(void) {}; + static inline int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset)