diff mbox series

[v4,03/12] mm: Introduce memfile_notifier

Message ID 20220118132121.31388-4-chao.p.peng@linux.intel.com (mailing list archive)
State New
Headers show
Series KVM: mm: fd-based approach for supporting KVM guest private memory | expand

Commit Message

Chao Peng Jan. 18, 2022, 1:21 p.m. UTC 
This patch introduces memfile_notifier facility so existing memory file
subsystems (e.g. tmpfs/hugetlbfs) can provide memory pages to allow a
third kernel component to make use of memory bookmarked in the memory
file and gets notified when the pages in the memory file become
allocated/invalidated.

It will be used for KVM to use a file descriptor as the guest memory
backing store and KVM will use this memfile_notifier interface to
interact with memory file subsystems. In the future there might be other
consumers (e.g. VFIO with encrypted device memory).

It consists two sets of callbacks:
  - memfile_notifier_ops: callbacks for memory backing store to notify
    KVM when memory gets allocated/invalidated.
  - memfile_pfn_ops: callbacks for KVM to call into memory backing store
    to request memory pages for guest private memory.

Userspace is in charge of guest memory lifecycle: it first allocates
pages in memory backing store and then passes the fd to KVM and lets KVM
register each memory slot to memory backing store via
memfile_register_notifier.

The supported memory backing store should maintain a memfile_notifier list
and provide routine for memfile_notifier to get the list head address and
memfile_pfn_ops callbacks for memfile_register_notifier. It also should call
memfile_notifier_fallocate/memfile_notifier_invalidate when the bookmarked
memory gets allocated/invalidated.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
 include/linux/memfile_notifier.h | 53 +++++++++++++++++++
 mm/Kconfig                       |  4 ++
 mm/Makefile                      |  1 +
 mm/memfile_notifier.c            | 89 ++++++++++++++++++++++++++++++++
 4 files changed, 147 insertions(+)
 create mode 100644 include/linux/memfile_notifier.h
 create mode 100644 mm/memfile_notifier.c

Comments

Vlastimil Babka March 7, 2022, 3:42 p.m. UTC | #1 
On 1/18/22 14:21, Chao Peng wrote:
> This patch introduces memfile_notifier facility so existing memory file
> subsystems (e.g. tmpfs/hugetlbfs) can provide memory pages to allow a
> third kernel component to make use of memory bookmarked in the memory
> file and gets notified when the pages in the memory file become
> allocated/invalidated.
> 
> It will be used for KVM to use a file descriptor as the guest memory
> backing store and KVM will use this memfile_notifier interface to
> interact with memory file subsystems. In the future there might be other
> consumers (e.g. VFIO with encrypted device memory).
> 
> It consists two sets of callbacks:
>   - memfile_notifier_ops: callbacks for memory backing store to notify
>     KVM when memory gets allocated/invalidated.
>   - memfile_pfn_ops: callbacks for KVM to call into memory backing store
>     to request memory pages for guest private memory.
> 
> Userspace is in charge of guest memory lifecycle: it first allocates
> pages in memory backing store and then passes the fd to KVM and lets KVM
> register each memory slot to memory backing store via
> memfile_register_notifier.
> 
> The supported memory backing store should maintain a memfile_notifier list
> and provide routine for memfile_notifier to get the list head address and
> memfile_pfn_ops callbacks for memfile_register_notifier. It also should call
> memfile_notifier_fallocate/memfile_notifier_invalidate when the bookmarked
> memory gets allocated/invalidated.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Process nitpick:
Here and in patch 4/12 you have Kirill's S-o-b so there should probably be
also "From: Kirill ..." as was in v3? Or in case you modified the original
patches so much to become the primary author, you should add
"Co-developed-by: Kirill ..." here before his S-o-b.

> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> ---
>  include/linux/memfile_notifier.h | 53 +++++++++++++++++++
>  mm/Kconfig                       |  4 ++
>  mm/Makefile                      |  1 +
>  mm/memfile_notifier.c            | 89 ++++++++++++++++++++++++++++++++
>  4 files changed, 147 insertions(+)
>  create mode 100644 include/linux/memfile_notifier.h
>  create mode 100644 mm/memfile_notifier.c
> 
> diff --git a/include/linux/memfile_notifier.h b/include/linux/memfile_notifier.h
> new file mode 100644
> index 000000000000..a03bebdd1322
> --- /dev/null
> +++ b/include/linux/memfile_notifier.h
> @@ -0,0 +1,53 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_MEMFILE_NOTIFIER_H
> +#define _LINUX_MEMFILE_NOTIFIER_H
> +
> +#include <linux/rculist.h>
> +#include <linux/spinlock.h>
> +#include <linux/srcu.h>
> +#include <linux/fs.h>
> +
> +struct memfile_notifier;
> +
> +struct memfile_notifier_ops {
> +	void (*invalidate)(struct memfile_notifier *notifier,
> +			   pgoff_t start, pgoff_t end);
> +	void (*fallocate)(struct memfile_notifier *notifier,
> +			  pgoff_t start, pgoff_t end);
> +};
> +
> +struct memfile_pfn_ops {
> +	long (*get_lock_pfn)(struct inode *inode, pgoff_t offset, int *order);
> +	void (*put_unlock_pfn)(unsigned long pfn);
> +};
> +
> +struct memfile_notifier {
> +	struct list_head list;
> +	struct memfile_notifier_ops *ops;
> +};
> +
> +struct memfile_notifier_list {
> +	struct list_head head;
> +	spinlock_t lock;
> +};
> +
> +#ifdef CONFIG_MEMFILE_NOTIFIER
> +static inline void memfile_notifier_list_init(struct memfile_notifier_list *list)
> +{
> +	INIT_LIST_HEAD(&list->head);
> +	spin_lock_init(&list->lock);
> +}
> +
> +extern void memfile_notifier_invalidate(struct memfile_notifier_list *list,
> +					pgoff_t start, pgoff_t end);
> +extern void memfile_notifier_fallocate(struct memfile_notifier_list *list,
> +				       pgoff_t start, pgoff_t end);
> +extern int memfile_register_notifier(struct inode *inode,
> +				     struct memfile_notifier *notifier,
> +				     struct memfile_pfn_ops **pfn_ops);
> +extern void memfile_unregister_notifier(struct inode *inode,
> +					struct memfile_notifier *notifier);
> +
> +#endif /* CONFIG_MEMFILE_NOTIFIER */
> +
> +#endif /* _LINUX_MEMFILE_NOTIFIER_H */
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 28edafc820ad..fa31eda3c895 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -900,6 +900,10 @@ config IO_MAPPING
>  config SECRETMEM
>  	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
>  
> +config MEMFILE_NOTIFIER
> +	bool
> +	select SRCU
> +
>  source "mm/damon/Kconfig"
>  
>  endmenu
> diff --git a/mm/Makefile b/mm/Makefile
> index d6c0042e3aa0..80588f7c3bc2 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -130,3 +130,4 @@ obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
>  obj-$(CONFIG_IO_MAPPING) += io-mapping.o
>  obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
>  obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
> +obj-$(CONFIG_MEMFILE_NOTIFIER) += memfile_notifier.o
> diff --git a/mm/memfile_notifier.c b/mm/memfile_notifier.c
> new file mode 100644
> index 000000000000..8171d4601a04
> --- /dev/null
> +++ b/mm/memfile_notifier.c
> @@ -0,0 +1,89 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + *  linux/mm/memfile_notifier.c
> + *
> + *  Copyright (C) 2022  Intel Corporation.
> + *             Chao Peng <chao.p.peng@linux.intel.com>
> + */
> +
> +#include <linux/memfile_notifier.h>
> +#include <linux/srcu.h>
> +
> +DEFINE_STATIC_SRCU(srcu);
> +
> +void memfile_notifier_invalidate(struct memfile_notifier_list *list,
> +				 pgoff_t start, pgoff_t end)
> +{
> +	struct memfile_notifier *notifier;
> +	int id;
> +
> +	id = srcu_read_lock(&srcu);
> +	list_for_each_entry_srcu(notifier, &list->head, list,
> +				 srcu_read_lock_held(&srcu)) {
> +		if (notifier->ops && notifier->ops->invalidate)
> +			notifier->ops->invalidate(notifier, start, end);
> +	}
> +	srcu_read_unlock(&srcu, id);
> +}
> +
> +void memfile_notifier_fallocate(struct memfile_notifier_list *list,
> +				pgoff_t start, pgoff_t end)
> +{
> +	struct memfile_notifier *notifier;
> +	int id;
> +
> +	id = srcu_read_lock(&srcu);
> +	list_for_each_entry_srcu(notifier, &list->head, list,
> +				 srcu_read_lock_held(&srcu)) {
> +		if (notifier->ops && notifier->ops->fallocate)
> +			notifier->ops->fallocate(notifier, start, end);
> +	}
> +	srcu_read_unlock(&srcu, id);
> +}
> +
> +static int memfile_get_notifier_info(struct inode *inode,
> +				     struct memfile_notifier_list **list,
> +				     struct memfile_pfn_ops **ops)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +int memfile_register_notifier(struct inode *inode,
> +			      struct memfile_notifier *notifier,
> +			      struct memfile_pfn_ops **pfn_ops)
> +{
> +	struct memfile_notifier_list *list;
> +	int ret;
> +
> +	if (!inode || !notifier | !pfn_ops)
> +		return -EINVAL;
> +
> +	ret = memfile_get_notifier_info(inode, &list, pfn_ops);
> +	if (ret)
> +		return ret;
> +
> +	spin_lock(&list->lock);
> +	list_add_rcu(&notifier->list, &list->head);
> +	spin_unlock(&list->lock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(memfile_register_notifier);
> +
> +void memfile_unregister_notifier(struct inode *inode,
> +				 struct memfile_notifier *notifier)
> +{
> +	struct memfile_notifier_list *list;
> +
> +	if (!inode || !notifier)
> +		return;
> +
> +	BUG_ON(memfile_get_notifier_info(inode, &list, NULL));
> +
> +	spin_lock(&list->lock);
> +	list_del_rcu(&notifier->list);
> +	spin_unlock(&list->lock);
> +
> +	synchronize_srcu(&srcu);
> +}
> +EXPORT_SYMBOL_GPL(memfile_unregister_notifier);
Chao Peng March 8, 2022, 1:45 a.m. UTC | #2 
On Mon, Mar 07, 2022 at 04:42:08PM +0100, Vlastimil Babka wrote:
> On 1/18/22 14:21, Chao Peng wrote:
> > This patch introduces memfile_notifier facility so existing memory file
> > subsystems (e.g. tmpfs/hugetlbfs) can provide memory pages to allow a
> > third kernel component to make use of memory bookmarked in the memory
> > file and gets notified when the pages in the memory file become
> > allocated/invalidated.
> > 
> > It will be used for KVM to use a file descriptor as the guest memory
> > backing store and KVM will use this memfile_notifier interface to
> > interact with memory file subsystems. In the future there might be other
> > consumers (e.g. VFIO with encrypted device memory).
> > 
> > It consists two sets of callbacks:
> >   - memfile_notifier_ops: callbacks for memory backing store to notify
> >     KVM when memory gets allocated/invalidated.
> >   - memfile_pfn_ops: callbacks for KVM to call into memory backing store
> >     to request memory pages for guest private memory.
> > 
> > Userspace is in charge of guest memory lifecycle: it first allocates
> > pages in memory backing store and then passes the fd to KVM and lets KVM
> > register each memory slot to memory backing store via
> > memfile_register_notifier.
> > 
> > The supported memory backing store should maintain a memfile_notifier list
> > and provide routine for memfile_notifier to get the list head address and
> > memfile_pfn_ops callbacks for memfile_register_notifier. It also should call
> > memfile_notifier_fallocate/memfile_notifier_invalidate when the bookmarked
> > memory gets allocated/invalidated.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> 
> Process nitpick:
> Here and in patch 4/12 you have Kirill's S-o-b so there should probably be
> also "From: Kirill ..." as was in v3? Or in case you modified the original
> patches so much to become the primary author, you should add
> "Co-developed-by: Kirill ..." here before his S-o-b.

Thanks. 3/12 is vastly rewritten so the latter case can be applied.
4/12 should keep Kirill as the primary author.

Chao
diff mbox series

Patch

diff --git a/include/linux/memfile_notifier.h b/include/linux/memfile_notifier.h
new file mode 100644
index 000000000000..a03bebdd1322
--- /dev/null
+++ b/include/linux/memfile_notifier.h
@@ -0,0 +1,53 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MEMFILE_NOTIFIER_H
+#define _LINUX_MEMFILE_NOTIFIER_H
+
+#include <linux/rculist.h>
+#include <linux/spinlock.h>
+#include <linux/srcu.h>
+#include <linux/fs.h>
+
+struct memfile_notifier;
+
+struct memfile_notifier_ops {
+	void (*invalidate)(struct memfile_notifier *notifier,
+			   pgoff_t start, pgoff_t end);
+	void (*fallocate)(struct memfile_notifier *notifier,
+			  pgoff_t start, pgoff_t end);
+};
+
+struct memfile_pfn_ops {
+	long (*get_lock_pfn)(struct inode *inode, pgoff_t offset, int *order);
+	void (*put_unlock_pfn)(unsigned long pfn);
+};
+
+struct memfile_notifier {
+	struct list_head list;
+	struct memfile_notifier_ops *ops;
+};
+
+struct memfile_notifier_list {
+	struct list_head head;
+	spinlock_t lock;
+};
+
+#ifdef CONFIG_MEMFILE_NOTIFIER
+static inline void memfile_notifier_list_init(struct memfile_notifier_list *list)
+{
+	INIT_LIST_HEAD(&list->head);
+	spin_lock_init(&list->lock);
+}
+
+extern void memfile_notifier_invalidate(struct memfile_notifier_list *list,
+					pgoff_t start, pgoff_t end);
+extern void memfile_notifier_fallocate(struct memfile_notifier_list *list,
+				       pgoff_t start, pgoff_t end);
+extern int memfile_register_notifier(struct inode *inode,
+				     struct memfile_notifier *notifier,
+				     struct memfile_pfn_ops **pfn_ops);
+extern void memfile_unregister_notifier(struct inode *inode,
+					struct memfile_notifier *notifier);
+
+#endif /* CONFIG_MEMFILE_NOTIFIER */
+
+#endif /* _LINUX_MEMFILE_NOTIFIER_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index 28edafc820ad..fa31eda3c895 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -900,6 +900,10 @@  config IO_MAPPING
 config SECRETMEM
 	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
 
+config MEMFILE_NOTIFIER
+	bool
+	select SRCU
+
 source "mm/damon/Kconfig"
 
 endmenu
diff --git a/mm/Makefile b/mm/Makefile
index d6c0042e3aa0..80588f7c3bc2 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -130,3 +130,4 @@  obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
 obj-$(CONFIG_IO_MAPPING) += io-mapping.o
 obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
 obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
+obj-$(CONFIG_MEMFILE_NOTIFIER) += memfile_notifier.o
diff --git a/mm/memfile_notifier.c b/mm/memfile_notifier.c
new file mode 100644
index 000000000000..8171d4601a04
--- /dev/null
+++ b/mm/memfile_notifier.c
@@ -0,0 +1,89 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/mm/memfile_notifier.c
+ *
+ *  Copyright (C) 2022  Intel Corporation.
+ *             Chao Peng <chao.p.peng@linux.intel.com>
+ */
+
+#include <linux/memfile_notifier.h>
+#include <linux/srcu.h>
+
+DEFINE_STATIC_SRCU(srcu);
+
+void memfile_notifier_invalidate(struct memfile_notifier_list *list,
+				 pgoff_t start, pgoff_t end)
+{
+	struct memfile_notifier *notifier;
+	int id;
+
+	id = srcu_read_lock(&srcu);
+	list_for_each_entry_srcu(notifier, &list->head, list,
+				 srcu_read_lock_held(&srcu)) {
+		if (notifier->ops && notifier->ops->invalidate)
+			notifier->ops->invalidate(notifier, start, end);
+	}
+	srcu_read_unlock(&srcu, id);
+}
+
+void memfile_notifier_fallocate(struct memfile_notifier_list *list,
+				pgoff_t start, pgoff_t end)
+{
+	struct memfile_notifier *notifier;
+	int id;
+
+	id = srcu_read_lock(&srcu);
+	list_for_each_entry_srcu(notifier, &list->head, list,
+				 srcu_read_lock_held(&srcu)) {
+		if (notifier->ops && notifier->ops->fallocate)
+			notifier->ops->fallocate(notifier, start, end);
+	}
+	srcu_read_unlock(&srcu, id);
+}
+
+static int memfile_get_notifier_info(struct inode *inode,
+				     struct memfile_notifier_list **list,
+				     struct memfile_pfn_ops **ops)
+{
+	return -EOPNOTSUPP;
+}
+
+int memfile_register_notifier(struct inode *inode,
+			      struct memfile_notifier *notifier,
+			      struct memfile_pfn_ops **pfn_ops)
+{
+	struct memfile_notifier_list *list;
+	int ret;
+
+	if (!inode || !notifier | !pfn_ops)
+		return -EINVAL;
+
+	ret = memfile_get_notifier_info(inode, &list, pfn_ops);
+	if (ret)
+		return ret;
+
+	spin_lock(&list->lock);
+	list_add_rcu(&notifier->list, &list->head);
+	spin_unlock(&list->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(memfile_register_notifier);
+
+void memfile_unregister_notifier(struct inode *inode,
+				 struct memfile_notifier *notifier)
+{
+	struct memfile_notifier_list *list;
+
+	if (!inode || !notifier)
+		return;
+
+	BUG_ON(memfile_get_notifier_info(inode, &list, NULL));
+
+	spin_lock(&list->lock);
+	list_del_rcu(&notifier->list);
+	spin_unlock(&list->lock);
+
+	synchronize_srcu(&srcu);
+}
+EXPORT_SYMBOL_GPL(memfile_unregister_notifier);