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charset="utf-8" Track guest_memfd memory's shareability status within the inode as opposed to the file, since it is property of the guest_memfd's memory contents. Shareability is a property of the memory and is indexed using the page's index in the inode. Because shareability is the memory's property, it is stored within guest_memfd instead of within KVM, like in kvm->mem_attr_array. KVM_MEMORY_ATTRIBUTE_PRIVATE in kvm->mem_attr_array must still be retained to allow VMs to only use guest_memfd for private memory and some other memory for shared memory. Not all use cases require guest_memfd() to be shared with the host when first created. Add a new flag, GUEST_MEMFD_FLAG_INIT_PRIVATE, which when set on KVM_CREATE_GUEST_MEMFD, initializes the memory as private to the guest, and therefore not mappable by the host. Otherwise, memory is shared until explicitly converted to private. Signed-off-by: Ackerley Tng Co-developed-by: Vishal Annapurve Signed-off-by: Vishal Annapurve Co-developed-by: Fuad Tabba Signed-off-by: Fuad Tabba Change-Id: If03609cbab3ad1564685c85bdba6dcbb6b240c0f --- Documentation/virt/kvm/api.rst | 5 ++ include/uapi/linux/kvm.h | 2 + virt/kvm/guest_memfd.c | 124 ++++++++++++++++++++++++++++++++- 3 files changed, 129 insertions(+), 2 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 86f74ce7f12a..f609337ae1c2 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6408,6 +6408,11 @@ belonging to the slot via its userspace_addr. The use of GUEST_MEMFD_FLAG_SUPPORT_SHARED will not be allowed for CoCo VM= s. This is validated when the guest_memfd instance is bound to the VM. =20 +If the capability KVM_CAP_GMEM_CONVERSIONS is supported, then the 'flags' = field +supports GUEST_MEMFD_FLAG_INIT_PRIVATE. Setting GUEST_MEMFD_FLAG_INIT_PRI= VATE +will initialize the memory for the guest_memfd as guest-only and not fault= able +by the host. + See KVM_SET_USER_MEMORY_REGION2 for additional details. =20 4.143 KVM_PRE_FAULT_MEMORY diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 4cc824a3a7c9..d7df312479aa 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1567,7 +1567,9 @@ struct kvm_memory_attributes { #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) =20 #define KVM_CREATE_GUEST_MEMFD _IOWR(KVMIO, 0xd4, struct kvm_create_guest= _memfd) + #define GUEST_MEMFD_FLAG_SUPPORT_SHARED (1UL << 0) +#define GUEST_MEMFD_FLAG_INIT_PRIVATE (1UL << 1) =20 struct kvm_create_guest_memfd { __u64 size; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 239d0f13dcc1..590932499eba 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -4,6 +4,7 @@ #include #include #include +#include #include #include =20 @@ -17,6 +18,24 @@ struct kvm_gmem { struct list_head entry; }; =20 +struct kvm_gmem_inode_private { +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + struct maple_tree shareability; +#endif +}; + +enum shareability { + SHAREABILITY_GUEST =3D 1, /* Only the guest can map (fault) folios in thi= s range. */ + SHAREABILITY_ALL =3D 2, /* Both guest and host can fault folios in this r= ange. */ +}; + +static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index= ); + +static struct kvm_gmem_inode_private *kvm_gmem_private(struct inode *inode) +{ + return inode->i_mapping->i_private_data; +} + /** * folio_file_pfn - like folio_file_page, but return a pfn. * @folio: The folio which contains this index. @@ -29,6 +48,58 @@ static inline kvm_pfn_t folio_file_pfn(struct folio *fol= io, pgoff_t index) return folio_pfn(folio) + (index & (folio_nr_pages(folio) - 1)); } =20 +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + +static int kvm_gmem_shareability_setup(struct kvm_gmem_inode_private *priv= ate, + loff_t size, u64 flags) +{ + enum shareability m; + pgoff_t last; + + last =3D (size >> PAGE_SHIFT) - 1; + m =3D flags & GUEST_MEMFD_FLAG_INIT_PRIVATE ? SHAREABILITY_GUEST : + SHAREABILITY_ALL; + return mtree_store_range(&private->shareability, 0, last, xa_mk_value(m), + GFP_KERNEL); +} + +static enum shareability kvm_gmem_shareability_get(struct inode *inode, + pgoff_t index) +{ + struct maple_tree *mt; + void *entry; + + mt =3D &kvm_gmem_private(inode)->shareability; + entry =3D mtree_load(mt, index); + WARN(!entry, + "Shareability should always be defined for all indices in inode."); + + return xa_to_value(entry); +} + +static struct folio *kvm_gmem_get_shared_folio(struct inode *inode, pgoff_= t index) +{ + if (kvm_gmem_shareability_get(inode, index) !=3D SHAREABILITY_ALL) + return ERR_PTR(-EACCES); + + return kvm_gmem_get_folio(inode, index); +} + +#else + +static int kvm_gmem_shareability_setup(struct maple_tree *mt, loff_t size,= u64 flags) +{ + return 0; +} + +static inline struct folio *kvm_gmem_get_shared_folio(struct inode *inode,= pgoff_t index) +{ + WARN_ONCE("Unexpected call to get shared folio.") + return NULL; +} + +#endif /* CONFIG_KVM_GMEM_SHARED_MEM */ + static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slo= t *slot, pgoff_t index, struct folio *folio) { @@ -333,7 +404,7 @@ static vm_fault_t kvm_gmem_fault_shared(struct vm_fault= *vmf) =20 filemap_invalidate_lock_shared(inode->i_mapping); =20 - folio =3D kvm_gmem_get_folio(inode, vmf->pgoff); + folio =3D kvm_gmem_get_shared_folio(inode, vmf->pgoff); if (IS_ERR(folio)) { int err =3D PTR_ERR(folio); =20 @@ -420,8 +491,33 @@ static struct file_operations kvm_gmem_fops =3D { .fallocate =3D kvm_gmem_fallocate, }; =20 +static void kvm_gmem_free_inode(struct inode *inode) +{ + struct kvm_gmem_inode_private *private =3D kvm_gmem_private(inode); + + kfree(private); + + free_inode_nonrcu(inode); +} + +static void kvm_gmem_destroy_inode(struct inode *inode) +{ + struct kvm_gmem_inode_private *private =3D kvm_gmem_private(inode); + +#ifdef CONFIG_KVM_GMEM_SHARED_MEM + /* + * mtree_destroy() can't be used within rcu callback, hence can't be + * done in ->free_inode(). + */ + if (private) + mtree_destroy(&private->shareability); +#endif +} + static const struct super_operations kvm_gmem_super_operations =3D { .statfs =3D simple_statfs, + .destroy_inode =3D kvm_gmem_destroy_inode, + .free_inode =3D kvm_gmem_free_inode, }; =20 static int kvm_gmem_init_fs_context(struct fs_context *fc) @@ -549,12 +645,26 @@ static const struct inode_operations kvm_gmem_iops = =3D { static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, loff_t size, u64 flags) { + struct kvm_gmem_inode_private *private; struct inode *inode; + int err; =20 inode =3D alloc_anon_secure_inode(kvm_gmem_mnt->mnt_sb, name); if (IS_ERR(inode)) return inode; =20 + err =3D -ENOMEM; + private =3D kzalloc(sizeof(*private), GFP_KERNEL); + if (!private) + goto out; + + mt_init(&private->shareability); + inode->i_mapping->i_private_data =3D private; + + err =3D kvm_gmem_shareability_setup(private, size, flags); + if (err) + goto out; + inode->i_private =3D (void *)(unsigned long)flags; inode->i_op =3D &kvm_gmem_iops; inode->i_mapping->a_ops =3D &kvm_gmem_aops; @@ -566,6 +676,11 @@ static struct inode *kvm_gmem_inode_make_secure_inode(= const char *name, WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); =20 return inode; + +out: + iput(inode); + + return ERR_PTR(err); } =20 static struct file *kvm_gmem_inode_create_getfile(void *priv, loff_t size, @@ -654,6 +769,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_= guest_memfd *args) if (kvm_arch_vm_supports_gmem_shared_mem(kvm)) valid_flags |=3D GUEST_MEMFD_FLAG_SUPPORT_SHARED; =20 + if (flags & GUEST_MEMFD_FLAG_SUPPORT_SHARED) + valid_flags |=3D GUEST_MEMFD_FLAG_INIT_PRIVATE; + if (flags & ~valid_flags) return -EINVAL; =20 @@ -842,6 +960,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory= _slot *slot, if (!file) return -EFAULT; =20 + filemap_invalidate_lock_shared(file_inode(file)->i_mapping); + folio =3D __kvm_gmem_get_pfn(file, slot, index, pfn, &is_prepared, max_or= der); if (IS_ERR(folio)) { r =3D PTR_ERR(folio); @@ -857,8 +977,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory= _slot *slot, *page =3D folio_file_page(folio, index); else folio_put(folio); - out: + filemap_invalidate_unlock_shared(file_inode(file)->i_mapping); fput(file); return r; } --=20 2.49.0.1045.g170613ef41-goog