[v9] Add NUMA mempolicy support for KVM guest-memfd

[PATCH V9 5/7] KVM: guest_memfd: Add slab-allocated inode cache

Posted by Shivank Garg 2 months, 3 weeks ago

Add dedicated inode structure (kvm_gmem_inode_info) and slab-allocated
inode cache for guest memory backing, similar to how shmem handles inodes.

This adds the necessary allocation/destruction functions and prepares
for upcoming guest_memfd NUMA policy support changes.

Signed-off-by: Shivank Garg <shivankg@amd.com>
---
 virt/kvm/guest_memfd.c | 58 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index dabcc2317291..989e2b26b344 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -17,6 +17,15 @@ struct kvm_gmem {
 	struct list_head entry;
 };
 
+struct kvm_gmem_inode_info {
+	struct inode vfs_inode;
+};
+
+static inline struct kvm_gmem_inode_info *KVM_GMEM_I(struct inode *inode)
+{
+	return container_of(inode, struct kvm_gmem_inode_info, vfs_inode);
+}
+
 /**
  * folio_file_pfn - like folio_file_page, but return a pfn.
  * @folio: The folio which contains this index.
@@ -392,8 +401,33 @@ static struct file_operations kvm_gmem_fops = {
 	.fallocate	= kvm_gmem_fallocate,
 };
 
+static struct kmem_cache *kvm_gmem_inode_cachep;
+
+static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
+{
+	struct kvm_gmem_inode_info *info;
+
+	info = alloc_inode_sb(sb, kvm_gmem_inode_cachep, GFP_KERNEL);
+	if (!info)
+		return NULL;
+
+	return &info->vfs_inode;
+}
+
+static void kvm_gmem_destroy_inode(struct inode *inode)
+{
+}
+
+static void kvm_gmem_free_inode(struct inode *inode)
+{
+	kmem_cache_free(kvm_gmem_inode_cachep, KVM_GMEM_I(inode));
+}
+
 static const struct super_operations kvm_gmem_super_operations = {
 	.statfs		= simple_statfs,
+	.alloc_inode	= kvm_gmem_alloc_inode,
+	.destroy_inode	= kvm_gmem_destroy_inode,
+	.free_inode	= kvm_gmem_free_inode,
 };
 
 static int kvm_gmem_init_fs_context(struct fs_context *fc)
@@ -426,17 +460,37 @@ static int kvm_gmem_init_mount(void)
 	return 0;
 }
 
+static void kvm_gmem_init_inode(void *foo)
+{
+	struct kvm_gmem_inode_info *info = foo;
+
+	inode_init_once(&info->vfs_inode);
+}
+
 int kvm_gmem_init(struct module *module)
 {
-	kvm_gmem_fops.owner = module;
+	int ret;
 
-	return kvm_gmem_init_mount();
+	kvm_gmem_fops.owner = module;
+	kvm_gmem_inode_cachep = kmem_cache_create("kvm_gmem_inode_cache",
+						  sizeof(struct kvm_gmem_inode_info),
+						  0, SLAB_ACCOUNT,
+						  kvm_gmem_init_inode);
+	if (!kvm_gmem_inode_cachep)
+		return -ENOMEM;
+	ret = kvm_gmem_init_mount();
+	if (ret) {
+		kmem_cache_destroy(kvm_gmem_inode_cachep);
+		return ret;
+	}
+	return 0;
 }
 
 void kvm_gmem_exit(void)
 {
 	kern_unmount(kvm_gmem_mnt);
 	kvm_gmem_mnt = NULL;
+	kmem_cache_destroy(kvm_gmem_inode_cachep);
 }
 
 static int kvm_gmem_migrate_folio(struct address_space *mapping,
-- 
2.43.0

Re: [PATCH V9 5/7] KVM: guest_memfd: Add slab-allocated inode cache

Posted by Vlastimil Babka 2 months, 2 weeks ago

On 7/13/25 19:43, Shivank Garg wrote:
> Add dedicated inode structure (kvm_gmem_inode_info) and slab-allocated
> inode cache for guest memory backing, similar to how shmem handles inodes.
> 
> This adds the necessary allocation/destruction functions and prepares
> for upcoming guest_memfd NUMA policy support changes.
> 
> Signed-off-by: Shivank Garg <shivankg@amd.com>
> ---
>  virt/kvm/guest_memfd.c | 58 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 56 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index dabcc2317291..989e2b26b344 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -17,6 +17,15 @@ struct kvm_gmem {
>  	struct list_head entry;
>  };
>  
> +struct kvm_gmem_inode_info {
> +	struct inode vfs_inode;
> +};
> +
> +static inline struct kvm_gmem_inode_info *KVM_GMEM_I(struct inode *inode)
> +{
> +	return container_of(inode, struct kvm_gmem_inode_info, vfs_inode);
> +}
> +
>  /**
>   * folio_file_pfn - like folio_file_page, but return a pfn.
>   * @folio: The folio which contains this index.
> @@ -392,8 +401,33 @@ static struct file_operations kvm_gmem_fops = {
>  	.fallocate	= kvm_gmem_fallocate,
>  };
>  
> +static struct kmem_cache *kvm_gmem_inode_cachep;
> +
> +static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
> +{
> +	struct kvm_gmem_inode_info *info;
> +
> +	info = alloc_inode_sb(sb, kvm_gmem_inode_cachep, GFP_KERNEL);
> +	if (!info)
> +		return NULL;
> +
> +	return &info->vfs_inode;
> +}
> +
> +static void kvm_gmem_destroy_inode(struct inode *inode)
> +{
> +}
> +
> +static void kvm_gmem_free_inode(struct inode *inode)
> +{
> +	kmem_cache_free(kvm_gmem_inode_cachep, KVM_GMEM_I(inode));
> +}
> +
>  static const struct super_operations kvm_gmem_super_operations = {
>  	.statfs		= simple_statfs,
> +	.alloc_inode	= kvm_gmem_alloc_inode,
> +	.destroy_inode	= kvm_gmem_destroy_inode,
> +	.free_inode	= kvm_gmem_free_inode,
>  };
>  
>  static int kvm_gmem_init_fs_context(struct fs_context *fc)
> @@ -426,17 +460,37 @@ static int kvm_gmem_init_mount(void)
>  	return 0;
>  }
>  
> +static void kvm_gmem_init_inode(void *foo)
> +{
> +	struct kvm_gmem_inode_info *info = foo;
> +
> +	inode_init_once(&info->vfs_inode);
> +}
> +
>  int kvm_gmem_init(struct module *module)
>  {
> -	kvm_gmem_fops.owner = module;
> +	int ret;
>  
> -	return kvm_gmem_init_mount();
> +	kvm_gmem_fops.owner = module;
> +	kvm_gmem_inode_cachep = kmem_cache_create("kvm_gmem_inode_cache",
> +						  sizeof(struct kvm_gmem_inode_info),
> +						  0, SLAB_ACCOUNT,
> +						  kvm_gmem_init_inode);

Since this is new code, please use the new variant of kmem_cache_create()
that takes the args parameter.

> +	if (!kvm_gmem_inode_cachep)
> +		return -ENOMEM;
> +	ret = kvm_gmem_init_mount();
> +	if (ret) {
> +		kmem_cache_destroy(kvm_gmem_inode_cachep);
> +		return ret;
> +	}
> +	return 0;
>  }
>  
>  void kvm_gmem_exit(void)
>  {
>  	kern_unmount(kvm_gmem_mnt);
>  	kvm_gmem_mnt = NULL;
> +	kmem_cache_destroy(kvm_gmem_inode_cachep);
>  }
>  
>  static int kvm_gmem_migrate_folio(struct address_space *mapping,

Re: [PATCH V9 5/7] KVM: guest_memfd: Add slab-allocated inode cache

Posted by Shivank Garg 2 months, 2 weeks ago


On 7/21/2025 5:14 PM, Vlastimil Babka wrote:
>> +	kvm_gmem_inode_cachep = kmem_cache_create("kvm_gmem_inode_cache",
>> +						  sizeof(struct kvm_gmem_inode_info),
>> +						  0, SLAB_ACCOUNT,
>> +						  kvm_gmem_init_inode);
> Since this is new code, please use the new variant of kmem_cache_create()
> that takes the args parameter.

Thank you for the review and suggestion.
I'll update this in the next version.