[RFC PATCH v5 11/16] KVM: guest_memfd: Pass KVM explicitly to provider attach

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Pass the attaching VM to the resource-provider attach callbacks. The
argument is valid during attachment and must not be retained. This
avoids storing the VM in the device binding context introduced next.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 include/linux/guest_memfd.h       | 3 ++-
 mm/shmem.c                        | 2 +-
 samples/kvm/mem_provider_sample.c | 2 +-
 virt/kvm/guest_memfd.c            | 9 +++++----
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/linux/guest_memfd.h b/include/linux/guest_memfd.h
index 79e2983c3b26..012174ad8ef8 100644
--- a/include/linux/guest_memfd.h
+++ b/include/linux/guest_memfd.h
@@ -12,6 +12,7 @@ struct file;
 struct folio;
 struct inode;
 struct mempolicy;
+struct kvm;
 
 /**
  * struct guest_memfd_handle - PFN information and an optional folio reference
@@ -110,7 +111,7 @@ struct guest_memfd_handle {
  * Used by filesystems and device drivers that provide memory for guest_memfd.
  */
 struct guest_memfd_provider_operations {
-	void *(*attach)(struct inode *gmem_inode, struct file *resource_file);
+	void *(*attach)(struct inode *gmem_inode, struct file *resource_file, struct kvm *kvm);
 	void (*release)(void *provider);
 	int (*prepare_memory_region)(void *provider, u64 offset, u64 size,
 				     u32 flags);
diff --git a/mm/shmem.c b/mm/shmem.c
index a1c1cc92515b..f652a6c1009f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5462,7 +5462,7 @@ static const struct inode_operations shmem_special_inode_operations = {
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 static void *shmem_gmem_attach(struct inode *gmem_inode,
-			       struct file *resource_file)
+		struct file *resource_file, struct kvm *kvm)
 {
 	struct inode *inode = file_inode(resource_file);
 	struct shmem_sb_info *sbinfo;
diff --git a/samples/kvm/mem_provider_sample.c b/samples/kvm/mem_provider_sample.c
index 4b7a8f760fdf..2eb9748cec5b 100644
--- a/samples/kvm/mem_provider_sample.c
+++ b/samples/kvm/mem_provider_sample.c
@@ -152,7 +152,7 @@ static long mps_file_ioctl(struct file *file, unsigned int cmd,
 }
 
 static void *mps_gmem_attach(struct inode *gmem_inode,
-			     struct file *resource_file)
+		struct file *resource_file, struct kvm *kvm)
 {
 	struct mps_info *info = resource_file->private_data;
 
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index ffecc4b19a17..178ac5ad123f 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -86,7 +86,7 @@ static bool kvm_gmem_is_pfn_mode(struct gmem_inode *gi)
 }
 
 static void *gmem_native_attach(struct inode *gmem_inode,
-				struct file *resource_file)
+		struct file *resource_file, struct kvm *kvm)
 {
 	return GMEM_I(gmem_inode);
 }
@@ -193,7 +193,8 @@ static void gmem_provider_init_ops(struct gmem_inode *gi,
 
 #define GMEM_RESOURCE_FD_NATIVE (-1)
 
-static int kvm_gmem_attach_resource(struct inode *inode, int resource_fd)
+static int kvm_gmem_attach_resource(struct kvm *kvm,
+		struct inode *inode, int resource_fd)
 {
 	struct gmem_inode *gi = GMEM_I(inode);
 	const struct guest_memfd_provider_operations *ops = NULL;
@@ -212,7 +213,7 @@ static int kvm_gmem_attach_resource(struct inode *inode, int resource_fd)
 	}
 
 	if (gmem_provider_ops_valid(gi, ops))
-		provider = ops->attach(inode, resource_file);
+		provider = ops->attach(inode, resource_file, kvm);
 
 	if (resource_file)
 		fput(resource_file);
@@ -1619,7 +1620,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags, int resour
 	 */
 	smp_wmb();
 
-	err = kvm_gmem_attach_resource(inode, resource_fd);
+	err = kvm_gmem_attach_resource(kvm, inode, resource_fd);
 	if (err) {
 		fput(file);
 		put_unused_fd(fd);
-- 
2.43.0