From: Nikita Kalyazin <[email protected]> write syscall populates guest_memfd with user-supplied data in a generic way, ie no vendor-specific preparation is performed. If the request is not page-aligned, the remaining bytes are initialised to 0.
write is only supported for non-CoCo setups where guest memory is not hardware-encrypted. Signed-off-by: Nikita Kalyazin <[email protected]> --- virt/kvm/guest_memfd.c | 48 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 94bafd6c558c..f4e218049afa 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -380,6 +380,8 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) static struct file_operations kvm_gmem_fops = { .mmap = kvm_gmem_mmap, + .llseek = default_llseek, + .write_iter = generic_perform_write, .open = generic_file_open, .release = kvm_gmem_release, .fallocate = kvm_gmem_fallocate, @@ -390,6 +392,49 @@ void kvm_gmem_init(struct module *module) kvm_gmem_fops.owner = module; } +static int kvm_kmem_gmem_write_begin(const struct kiocb *kiocb, + struct address_space *mapping, + loff_t pos, unsigned int len, + struct folio **foliop, + void **fsdata) +{ + struct file *file = kiocb->ki_filp; + struct inode *inode = file_inode(file); + pgoff_t index = pos >> PAGE_SHIFT; + struct folio *folio; + + if (!kvm_gmem_supports_mmap(inode)) + return -ENODEV; + + if (pos + len > i_size_read(inode)) + return -EINVAL; + + folio = kvm_gmem_get_folio(inode, index); + if (IS_ERR(folio)) + return -EFAULT; + + *foliop = folio; + return 0; +} + +static int kvm_kmem_gmem_write_end(const struct kiocb *kiocb, + struct address_space *mapping, + loff_t pos, unsigned int len, + unsigned int copied, + struct folio *folio, void *fsdata) +{ + if (copied && copied < len) { + unsigned int from = pos & ((1UL << folio_order(folio)) - 1); + + folio_zero_range(folio, from + copied, len - copied); + } + + folio_unlock(folio); + folio_put(folio); + + return copied; +} + static int kvm_gmem_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode) @@ -442,6 +487,8 @@ static void kvm_gmem_free_folio(struct folio *folio) static const struct address_space_operations kvm_gmem_aops = { .dirty_folio = noop_dirty_folio, + .write_begin = kvm_kmem_gmem_write_begin, + .write_end = kvm_kmem_gmem_write_end, .migrate_folio = kvm_gmem_migrate_folio, .error_remove_folio = kvm_gmem_error_folio, #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE @@ -489,6 +536,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) } file->f_flags |= O_LARGEFILE; + file->f_mode |= FMODE_LSEEK | FMODE_PWRITE; inode = file->f_inode; WARN_ON(file->f_mapping != inode->i_mapping); -- 2.50.1
