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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7F19B180002 X-Stat-Signature: 1z9mhxyxm1d49haqs78iqf64q6rcnhm7 X-Rspam-User: X-HE-Tag: 1749201142-3047 X-HE-Meta: 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 TBOJS4Y4 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 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: On 05.06.25 17:37, Fuad Tabba wrote: > This patch enables support for shared memory in guest_memfd, including > mapping that memory from host userspace. > > This functionality is gated by the KVM_GMEM_SHARED_MEM Kconfig option, > and enabled for a given instance by the GUEST_MEMFD_FLAG_SUPPORT_SHARED > flag at creation time. > > Co-developed-by: Ackerley Tng > Signed-off-by: Ackerley Tng > Signed-off-by: Fuad Tabba > --- [...] > +static bool kvm_gmem_supports_shared(struct inode *inode) > +{ > + u64 flags; > + > + if (!IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM)) > + return false; > + > + flags = (u64)inode->i_private; Can probably do above const u64 flags = (u64)inode->i_private; > + > + return flags & GUEST_MEMFD_FLAG_SUPPORT_SHARED; > +} > + > +static vm_fault_t kvm_gmem_fault_shared(struct vm_fault *vmf) > +{ > + struct inode *inode = file_inode(vmf->vma->vm_file); > + struct folio *folio; > + vm_fault_t ret = VM_FAULT_LOCKED; > + > + if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) > + return VM_FAULT_SIGBUS; > + > + folio = kvm_gmem_get_folio(inode, vmf->pgoff); > + if (IS_ERR(folio)) { > + int err = PTR_ERR(folio); > + > + if (err == -EAGAIN) > + return VM_FAULT_RETRY; > + > + return vmf_error(err); > + } > + > + if (WARN_ON_ONCE(folio_test_large(folio))) { > + ret = VM_FAULT_SIGBUS; > + goto out_folio; > + } > + > + if (!folio_test_uptodate(folio)) { > + clear_highpage(folio_page(folio, 0)); > + kvm_gmem_mark_prepared(folio); > + } > + > + vmf->page = folio_file_page(folio, vmf->pgoff); > + > +out_folio: > + if (ret != VM_FAULT_LOCKED) { > + folio_unlock(folio); > + folio_put(folio); > + } > + > + return ret; > +} > + > +static const struct vm_operations_struct kvm_gmem_vm_ops = { > + .fault = kvm_gmem_fault_shared, > +}; > + > +static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + if (!kvm_gmem_supports_shared(file_inode(file))) > + return -ENODEV; > + > + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) != > + (VM_SHARED | VM_MAYSHARE)) { > + return -EINVAL; > + } > + > + vma->vm_ops = &kvm_gmem_vm_ops; > + > + return 0; > +} > + > static struct file_operations kvm_gmem_fops = { > + .mmap = kvm_gmem_mmap, > .open = generic_file_open, > .release = kvm_gmem_release, > .fallocate = kvm_gmem_fallocate, > @@ -428,6 +500,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) > } > > file->f_flags |= O_LARGEFILE; > + allow_write_access(file); Why is that required? As the docs mention, it must be paired with a previous deny_write_access(). ... and I don't find similar usage anywhere else. Apart from that here Acked-by: David Hildenbrand -- Cheers, David / dhildenb