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AJvYcCWNB1NljW3jsmh+N3s4DL4NGr20KZifRLTthugQn23qMcyAZ4VxY6PLoxcg7RziCu49jZhue0tveaP3y/8xPds=@vger.kernel.org X-Gm-Message-State: AOJu0YxmOovJol6oIMrrFa5Hr0PReNH/xR1QxmkylK1B5CIv+OFLGabY dx1O/4fQ3FQoRS9djRoQ5BR16SV6KZ173Szu8JAwrhxCrQDfqWIn449HQ6K+zvLCXZCJbQ261om xhahCbx5ZIw== X-Google-Smtp-Source: AGHT+IGI9ILyUKepnXkdGGm63vJAAGDjSs8x0J8EEnoDiBvLz3VF49AsRx4LzlHZ8XR+aVVknzB+VH1DaL5H X-Received: from pjbsv11.prod.google.com ([2002:a17:90b:538b:b0:2f9:dc36:b11]) (user=afranji job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:56cc:b0:2fe:a8b1:7d8 with SMTP id 98e67ed59e1d1-30e7d5acb07mr6669924a91.25.1747423194396; Fri, 16 May 2025 12:19:54 -0700 (PDT) Date: Fri, 16 May 2025 19:19:24 +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: Subject: [RFC PATCH v2 04/13] KVM: guest_mem: Add ioctl KVM_LINK_GUEST_MEMFD 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 KVM_LINK_GUEST_MEMFD will link a gmem fd's underlying inode to a new file (and fd). Signed-off-by: Ackerley Tng Co-developed-by: Ryan Afranji Signed-off-by: Ryan Afranji --- include/uapi/linux/kvm.h | 8 ++++++ virt/kvm/guest_memfd.c | 57 ++++++++++++++++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 10 +++++++ virt/kvm/kvm_mm.h | 7 +++++ 4 files changed, 82 insertions(+) diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index c6988e2c68d5..8f17f0b462aa 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1583,4 +1583,12 @@ struct kvm_pre_fault_memory { __u64 padding[5]; }; +#define KVM_LINK_GUEST_MEMFD _IOWR(KVMIO, 0xd6, struct kvm_link_guest_memfd) + +struct kvm_link_guest_memfd { + __u64 fd; + __u64 flags; + __u64 reserved[6]; +}; + #endif /* __LINUX_KVM_H */ diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index a3918d1695b9..d76bd1119198 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -555,6 +555,63 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) return __kvm_gmem_create(kvm, size, flags); } +int kvm_gmem_link(struct kvm *kvm, struct kvm_link_guest_memfd *args) +{ + static const char *name = "[kvm-gmem]"; + u64 flags = args->flags; + u64 valid_flags = 0; + struct file *dst_file, *src_file; + struct kvm_gmem *gmem; + struct timespec64 ts; + struct inode *inode; + struct fd f; + int ret, fd; + + if (flags & ~valid_flags) + return -EINVAL; + + f = fdget(args->fd); + src_file = fd_file(f); + if (!src_file) + return -EINVAL; + + ret = -EINVAL; + if (src_file->f_op != &kvm_gmem_fops) + goto out; + + /* Cannot link a gmem file with the same vm again */ + gmem = src_file->private_data; + if (gmem->kvm == kvm) + goto out; + + ret = fd = get_unused_fd_flags(0); + if (ret < 0) + goto out; + + inode = file_inode(src_file); + dst_file = kvm_gmem_alloc_view(kvm, inode, name); + if (IS_ERR(dst_file)) { + ret = PTR_ERR(dst_file); + goto out_fd; + } + + ts = inode_set_ctime_current(inode); + inode_set_atime_to_ts(inode, ts); + + inc_nlink(inode); + ihold(inode); + + fd_install(fd, dst_file); + fdput(f); + return fd; + +out_fd: + put_unused_fd(fd); +out: + fdput(f); + return ret; +} + int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset) { diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1e3fd81868bc..a9b01841a243 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -5285,6 +5285,16 @@ static long kvm_vm_ioctl(struct file *filp, r = kvm_gmem_create(kvm, &guest_memfd); break; } + case KVM_LINK_GUEST_MEMFD: { + struct kvm_link_guest_memfd params; + + r = -EFAULT; + if (copy_from_user(¶ms, argp, sizeof(params))) + goto out; + + r = kvm_gmem_link(kvm, ¶ms); + break; + } #endif default: r = kvm_arch_vm_ioctl(filp, ioctl, arg); diff --git a/virt/kvm/kvm_mm.h b/virt/kvm/kvm_mm.h index dcacb76b8f00..85baf8a7e0de 100644 --- a/virt/kvm/kvm_mm.h +++ b/virt/kvm/kvm_mm.h @@ -71,6 +71,7 @@ static inline void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, 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_link(struct kvm *kvm, struct kvm_link_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); @@ -82,6 +83,12 @@ static inline int kvm_gmem_init(struct module *module) static inline void kvm_gmem_exit(void) {}; +static inline int kvm_gmem_link(struct kvm *kvm, + struct kvm_link_guest_memfd *args) +{ + return -EOPNOTSUPP; +} + static inline int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned int fd, loff_t offset)