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AJvYcCXjjQ9XrAu5kYNgkLHCaXIc836EDfHAhLI6+4K7eY7rFCru36VOy4ensZdn5XgUhDA243mofeuHrA==@kvack.org X-Gm-Message-State: AOJu0YzkJY8WK0Phq+kVM7HESOqF2wMMCameYhMovFP4okNlgvoV6IEj W1eYYmgm69iGXuBYKsRUXnzFFQX5cGe7yplmUmIhC2d0O5TozMjzkD+SMfvislDAZuFnaShvSQ= = X-Google-Smtp-Source: AGHT+IGngaZfLNR9G+mSoTgx2073MmGnWMrkl6EslGCWKeowY0DzmJkEF+mR9oXw1GyqKOgR3dKkpwK4uw== X-Received: from wmbay1.prod.google.com ([2002:a05:600c:1e01:b0:43d:9f1:31a9]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:c15:b0:43c:eeee:b713 with SMTP id 5b1f17b1804b1-43d85065ab9mr84209735e9.20.1743175897006; Fri, 28 Mar 2025 08:31:37 -0700 (PDT) Date: Fri, 28 Mar 2025 15:31:27 +0000 In-Reply-To: <20250328153133.3504118-1-tabba@google.com> Mime-Version: 1.0 References: <20250328153133.3504118-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250328153133.3504118-2-tabba@google.com> Subject: [PATCH v7 1/7] KVM: guest_memfd: Make guest mem use guest mem inodes instead of anonymous inodes From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, tabba@google.com X-Rspamd-Queue-Id: 62C4918001A X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 7g8e8z8xeu97s9sc35pezphax6hrax6a X-HE-Tag: 1743175898-103761 X-HE-Meta: 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 mPe5BDjC lVu7mjXThtNOkxX/0aoPY/EUwtwaYJR+Z8QMH9qCk8D6SBOhgiNdRkEZhAU7qo0bgr1s+TxVetVWboFoPRMT1eKkuchQPiVx0HA1yNslnZazM+qkD/OLYaZNyQmhjeqLSoIeKXFbUGN35u+YRrGMgbPfccU2z4vqD0z46z18nwC3bAbj39BGbmgpwig5RiF7bgkXDo7bKzc3d0yj+53elUIEEeGhvOjvRdAFLjj+xeoYNY1VE/8PT/eE8nz8vydoinqUlW8/HP+/99YRXt5uT50zf2OwTcgKTZbEYFoe+4nVQSV/p7460qfVcrVfwJQJK4Jg2HMNbUuqBozNQV1oNzxZA3Zw5yHH/WxA8j/R9ktbvYP8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 | 130 +++++++++++++++++++++++++++++++------ 2 files changed, 111 insertions(+), 20 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 fbf89e643add..844e70c82558 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; @@ -320,6 +324,38 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) return gfn - slot->base_gfn + slot->gmem.pgoff; } +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 void kvm_gmem_init_mount(void) +{ + kvm_gmem_mnt = kern_mount(&kvm_gmem_fs); + BUG_ON(IS_ERR(kvm_gmem_mnt)); + + /* For giggles. Userspace can never map this anyways. */ + kvm_gmem_mnt->mnt_flags |= MNT_NOEXEC; +} + #ifdef CONFIG_KVM_GMEM_SHARED_MEM static bool kvm_gmem_offset_is_shared(struct file *file, pgoff_t index) { @@ -430,6 +466,8 @@ static struct file_operations kvm_gmem_fops = { void kvm_gmem_init(struct module *module) { kvm_gmem_fops.owner = module; + + kvm_gmem_init_mount(); } static int kvm_gmem_migrate_folio(struct address_space *mapping, @@ -511,11 +549,79 @@ 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) +{ + const struct qstr qname = QSTR_INIT(name, strlen(name)); + struct inode *inode; + int err; + + inode = alloc_anon_inode(kvm_gmem_mnt->mnt_sb); + if (IS_ERR(inode)) + return inode; + + err = security_inode_init_security_anon(inode, &qname, NULL); + if (err) { + iput(inode); + return ERR_PTR(err); + } + + 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; @@ -529,32 +635,16 @@ 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;