[PATCH v2 0/4] Add iomem helpers for use from debugfs

[PATCH v2 0/4] Add iomem helpers for use from debugfs

[Michal Wajdeczko]

This series attempts to promote helpers used by Xe [1] to libfs.
Earlier attempt [2] with similar helper was unnoticed.

[1] https://patchwork.freedesktop.org/series/140848/#rev1
[2] https://patchwork.freedesktop.org/series/133507/#rev1

v1: https://patchwork.freedesktop.org/series/141060/#rev1
v2: use iterate_and_advance to treat user_iter separately (Matthew)

Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org

Michal Wajdeczko (4):
  iov_iter: Provide copy_iomem_to|from_iter()
  libfs: Provide simple_read_from|write_to_iomem()
  drm/xe: Add read/write debugfs helpers for GGTT node
  drm/xe/pf: Expose access to the VF GGTT PTEs over debugfs

 drivers/gpu/drm/xe/xe_ggtt.c                | 52 ++++++++++++++
 drivers/gpu/drm/xe/xe_ggtt.h                |  7 ++
 drivers/gpu/drm/xe/xe_gt_sriov_pf_debugfs.c | 62 ++++++++++++++++
 fs/libfs.c                                  | 78 +++++++++++++++++++++
 include/linux/fs.h                          |  5 ++
 include/linux/uio.h                         |  3 +
 lib/iov_iter.c                              | 66 +++++++++++++++++
 7 files changed, 273 insertions(+)

-- 
2.43.0

[PATCH v2 1/4] iov_iter: Provide copy_iomem_to|from_iter()

[Michal Wajdeczko]

Define simple copy helpers that work on I/O memory. This will
allow reuse of existing framework functions in new use cases.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
---
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
---
v2: use iterate_and_advance to treat user_iter separately (Matthew)
---
 include/linux/uio.h |  3 +++
 lib/iov_iter.c      | 66 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 853f9de5aa05..354a6b2d1e94 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -183,6 +183,9 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
 
+size_t copy_iomem_to_iter(const void __iomem *from, size_t bytes, struct iov_iter *i);
+size_t copy_iomem_from_iter(void __iomem *to, size_t bytes, struct iov_iter *i);
+
 static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
 		size_t bytes, struct iov_iter *i)
 {
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 908e75a28d90..80feff9c8875 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -323,6 +323,72 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 #endif
 
+static __always_inline
+size_t memcpy_iomem_to_iter(void *iter_to, size_t progress, size_t len,
+			    void *from, void *priv2)
+{
+	memcpy_fromio(iter_to, from + progress, len);
+	return 0;
+}
+
+static __always_inline
+size_t memcpy_iomem_from_iter(void *iter_from, size_t progress, size_t len,
+			      void *to, void *priv2)
+{
+	memcpy_toio(to + progress, iter_from, len);
+	return 0;
+}
+
+static __always_inline
+size_t copy_iomem_to_user_iter(void __user *iter_to, size_t progress,
+			       size_t len, void *from, void *priv2)
+{
+	unsigned char buf[SMP_CACHE_BYTES];
+	size_t chunk = min(len, sizeof(buf));
+
+	memcpy_fromio(buf, from + progress, chunk);
+	chunk -= copy_to_user_iter(iter_to, progress, chunk, buf, priv2);
+	return len - chunk;
+}
+
+static __always_inline
+size_t copy_iomem_from_user_iter(void __user *iter_from, size_t progress,
+				 size_t len, void *to, void *priv2)
+{
+	unsigned char buf[SMP_CACHE_BYTES];
+	size_t chunk = min(len, sizeof(buf));
+
+	chunk -= copy_from_user_iter(iter_from, progress, chunk, buf, priv2);
+	memcpy_toio(to, buf, chunk);
+	return len - chunk;
+}
+
+size_t copy_iomem_to_iter(const void __iomem *from, size_t bytes, struct iov_iter *i)
+{
+	if (WARN_ON_ONCE(i->data_source))
+		return 0;
+	if (user_backed_iter(i))
+		might_fault();
+
+	return iterate_and_advance(i, bytes, (void *)from,
+				   copy_iomem_to_user_iter,
+				   memcpy_iomem_to_iter);
+}
+EXPORT_SYMBOL(copy_iomem_to_iter);
+
+size_t copy_iomem_from_iter(void __iomem *to, size_t bytes, struct iov_iter *i)
+{
+	if (WARN_ON_ONCE(!i->data_source))
+		return 0;
+	if (user_backed_iter(i))
+		might_fault();
+
+	return iterate_and_advance(i, bytes, (void *)to,
+				   copy_iomem_from_user_iter,
+				   memcpy_iomem_from_iter);
+}
+EXPORT_SYMBOL(copy_iomem_from_iter);
+
 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 {
 	struct page *head;
-- 
2.43.0

[PATCH v2 2/4] libfs: Provide simple_read_from|write_to_iomem()

[Michal Wajdeczko]

New functions are similar to simple_read_from|write_to_buffer()
but work on the I/O memory instead. Will allow wider code reuse.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 fs/libfs.c         | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |  5 +++
 2 files changed, 83 insertions(+)

diff --git a/fs/libfs.c b/fs/libfs.c
index 46966fd8bcf9..1c7343f1147f 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1095,6 +1095,84 @@ void simple_release_fs(struct vfsmount **mount, int *count)
 }
 EXPORT_SYMBOL(simple_release_fs);
 
+/**
+ * simple_read_from_iomem() - copy data from the I/O memory to user space
+ * @to: the user space buffer to read to
+ * @count: the maximum number of bytes to read
+ * @ppos: the current position in the buffer
+ * @from: the I/O memory to read from
+ * @available: the size of the iomem memory
+ *
+ * The simple_read_from_iomem() function reads up to @count bytes from the
+ * I/O memory @from at offset @ppos into the user space address starting at @to.
+ *
+ * Return: On success, the number of bytes read is returned and the offset
+ * @ppos is advanced by this number, or negative value is returned on error.
+ */
+ssize_t simple_read_from_iomem(void __user *to, size_t count, loff_t *ppos,
+			       const void __iomem *from, size_t available)
+{
+	struct iov_iter iter;
+	loff_t pos = *ppos;
+	size_t copied;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	if (import_ubuf(ITER_DEST, to, count, &iter))
+		return -EFAULT;
+
+	copied = copy_iomem_to_iter(from + pos, count, &iter);
+	if (!copied)
+		return -EFAULT;
+
+	*ppos = pos + copied;
+	return copied;
+}
+EXPORT_SYMBOL(simple_read_from_iomem);
+
+/**
+ * simple_write_to_iomem() - copy data from user space to the I/O memory
+ * @to: the I/O memory to write to
+ * @available: the size of the I/O memory
+ * @ppos: the current position in the buffer
+ * @from: the user space buffer to read from
+ * @count: the maximum number of bytes to read
+ *
+ * The simple_write_to_iomem() function reads up to @count bytes from the user
+ * space address starting at @from into the I/O memory @to at offset @ppos.
+ *
+ * Return: On success, the number of bytes written is returned and the offset
+ * @ppos is advanced by this number, or negative value is returned on error.
+ */
+ssize_t simple_write_to_iomem(void __iomem *to, size_t available, loff_t *ppos,
+			      const void __user *from, size_t count)
+{
+	struct iov_iter iter;
+	loff_t pos = *ppos;
+	size_t copied;
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= available || !count)
+		return 0;
+	if (count > available - pos)
+		count = available - pos;
+	if (import_ubuf(ITER_SOURCE, (void __user *)from, count, &iter))
+		return -EFAULT;
+
+	copied = copy_iomem_from_iter(to + pos, count, &iter);
+	if (!copied)
+		return -EFAULT;
+
+	*ppos = pos + copied;
+	return copied;
+}
+EXPORT_SYMBOL(simple_write_to_iomem);
+
 /**
  * simple_read_from_buffer - copy data from the buffer to user space
  * @to: the user space buffer to read to
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3559446279c1..2cc73c5961b0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3426,6 +3426,11 @@ extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
 extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
 		const void __user *from, size_t count);
 
+ssize_t simple_read_from_iomem(void __user *to, size_t count, loff_t *ppos,
+			       const void __iomem *from, size_t available);
+ssize_t simple_write_to_iomem(void __iomem *to, size_t available, loff_t *ppos,
+			      const void __user *from, size_t count);
+
 struct offset_ctx {
 	struct maple_tree	mt;
 	unsigned long		next_offset;
-- 
2.43.0

Re: [PATCH v2 1/4] iov_iter: Provide copy_iomem_to|from_iter()

[kernel test robot]

Hi Michal,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-xe/drm-xe-next]
[also build test WARNING on brauner-vfs/vfs.all akpm-mm/mm-nonmm-unstable linus/master v6.12-rc7 next-20241113]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Michal-Wajdeczko/iov_iter-Provide-copy_iomem_to-from_iter/20241113-080831
base:   https://gitlab.freedesktop.org/drm/xe/kernel.git drm-xe-next
patch link:    https://lore.kernel.org/r/20241112200454.2211-2-michal.wajdeczko%40intel.com
patch subject: [PATCH v2 1/4] iov_iter: Provide copy_iomem_to|from_iter()
config: x86_64-randconfig-123-20241113 (https://download.01.org/0day-ci/archive/20241114/202411140935.iEbIWcpc-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241114/202411140935.iEbIWcpc-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411140935.iEbIWcpc-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> lib/iov_iter.c:373:47: sparse: sparse: cast removes address space '__iomem' of expression
   lib/iov_iter.c:386:47: sparse: sparse: cast removes address space '__iomem' of expression
>> lib/iov_iter.c:349:33: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const volatile [noderef] __iomem * @@     got void * @@
   lib/iov_iter.c:349:33: sparse:     expected void const volatile [noderef] __iomem *
   lib/iov_iter.c:349:33: sparse:     got void *
   lib/iov_iter.c:330:37: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const volatile [noderef] __iomem * @@     got void * @@
   lib/iov_iter.c:330:37: sparse:     expected void const volatile [noderef] __iomem *
   lib/iov_iter.c:330:37: sparse:     got void *
>> lib/iov_iter.c:362:21: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void volatile [noderef] __iomem * @@     got void *to @@
   lib/iov_iter.c:362:21: sparse:     expected void volatile [noderef] __iomem *
   lib/iov_iter.c:362:21: sparse:     got void *to
>> lib/iov_iter.c:338:24: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void volatile [noderef] __iomem * @@     got void * @@
   lib/iov_iter.c:338:24: sparse:     expected void volatile [noderef] __iomem *
   lib/iov_iter.c:338:24: sparse:     got void *

vim +/__iomem +373 lib/iov_iter.c

   333	
   334	static __always_inline
   335	size_t memcpy_iomem_from_iter(void *iter_from, size_t progress, size_t len,
   336				      void *to, void *priv2)
   337	{
 > 338		memcpy_toio(to + progress, iter_from, len);
   339		return 0;
   340	}
   341	
   342	static __always_inline
   343	size_t copy_iomem_to_user_iter(void __user *iter_to, size_t progress,
   344				       size_t len, void *from, void *priv2)
   345	{
   346		unsigned char buf[SMP_CACHE_BYTES];
   347		size_t chunk = min(len, sizeof(buf));
   348	
 > 349		memcpy_fromio(buf, from + progress, chunk);
   350		chunk -= copy_to_user_iter(iter_to, progress, chunk, buf, priv2);
   351		return len - chunk;
   352	}
   353	
   354	static __always_inline
   355	size_t copy_iomem_from_user_iter(void __user *iter_from, size_t progress,
   356					 size_t len, void *to, void *priv2)
   357	{
   358		unsigned char buf[SMP_CACHE_BYTES];
   359		size_t chunk = min(len, sizeof(buf));
   360	
   361		chunk -= copy_from_user_iter(iter_from, progress, chunk, buf, priv2);
 > 362		memcpy_toio(to, buf, chunk);
   363		return len - chunk;
   364	}
   365	
   366	size_t copy_iomem_to_iter(const void __iomem *from, size_t bytes, struct iov_iter *i)
   367	{
   368		if (WARN_ON_ONCE(i->data_source))
   369			return 0;
   370		if (user_backed_iter(i))
   371			might_fault();
   372	
 > 373		return iterate_and_advance(i, bytes, (void *)from,
   374					   copy_iomem_to_user_iter,
   375					   memcpy_iomem_to_iter);
   376	}
   377	EXPORT_SYMBOL(copy_iomem_to_iter);
   378	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 1/4] iov_iter: Provide copy_iomem_to|from_iter()

[kernel test robot]

Hi Michal,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-xe/drm-xe-next]
[also build test WARNING on brauner-vfs/vfs.all akpm-mm/mm-nonmm-unstable linus/master v6.12-rc7 next-20241113]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Michal-Wajdeczko/iov_iter-Provide-copy_iomem_to-from_iter/20241113-080831
base:   https://gitlab.freedesktop.org/drm/xe/kernel.git drm-xe-next
patch link:    https://lore.kernel.org/r/20241112200454.2211-2-michal.wajdeczko%40intel.com
patch subject: [PATCH v2 1/4] iov_iter: Provide copy_iomem_to|from_iter()
config: arm-randconfig-r113-20241113 (https://download.01.org/0day-ci/archive/20241114/202411141227.4kDiZIXM-lkp@intel.com/config)
compiler: clang version 16.0.6 (https://github.com/llvm/llvm-project 7cbf1a2591520c2491aa35339f227775f4d3adf6)
reproduce: (https://download.01.org/0day-ci/archive/20241114/202411141227.4kDiZIXM-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411141227.4kDiZIXM-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   lib/iov_iter.c:373:47: sparse: sparse: cast removes address space '__iomem' of expression
   lib/iov_iter.c:386:47: sparse: sparse: cast removes address space '__iomem' of expression
>> lib/iov_iter.c:349:9: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const volatile [noderef] __iomem *from @@     got void * @@
   lib/iov_iter.c:349:9: sparse:     expected void const volatile [noderef] __iomem *from
   lib/iov_iter.c:349:9: sparse:     got void *
   lib/iov_iter.c:330:9: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const volatile [noderef] __iomem *from @@     got void * @@
   lib/iov_iter.c:330:9: sparse:     expected void const volatile [noderef] __iomem *from
   lib/iov_iter.c:330:9: sparse:     got void *
>> lib/iov_iter.c:362:9: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void volatile [noderef] __iomem *to @@     got void *to @@
   lib/iov_iter.c:362:9: sparse:     expected void volatile [noderef] __iomem *to
   lib/iov_iter.c:362:9: sparse:     got void *to
>> lib/iov_iter.c:338:9: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void volatile [noderef] __iomem *to @@     got void * @@
   lib/iov_iter.c:338:9: sparse:     expected void volatile [noderef] __iomem *to
   lib/iov_iter.c:338:9: sparse:     got void *

vim +349 lib/iov_iter.c

   333	
   334	static __always_inline
   335	size_t memcpy_iomem_from_iter(void *iter_from, size_t progress, size_t len,
   336				      void *to, void *priv2)
   337	{
 > 338		memcpy_toio(to + progress, iter_from, len);
   339		return 0;
   340	}
   341	
   342	static __always_inline
   343	size_t copy_iomem_to_user_iter(void __user *iter_to, size_t progress,
   344				       size_t len, void *from, void *priv2)
   345	{
   346		unsigned char buf[SMP_CACHE_BYTES];
   347		size_t chunk = min(len, sizeof(buf));
   348	
 > 349		memcpy_fromio(buf, from + progress, chunk);
   350		chunk -= copy_to_user_iter(iter_to, progress, chunk, buf, priv2);
   351		return len - chunk;
   352	}
   353	
   354	static __always_inline
   355	size_t copy_iomem_from_user_iter(void __user *iter_from, size_t progress,
   356					 size_t len, void *to, void *priv2)
   357	{
   358		unsigned char buf[SMP_CACHE_BYTES];
   359		size_t chunk = min(len, sizeof(buf));
   360	
   361		chunk -= copy_from_user_iter(iter_from, progress, chunk, buf, priv2);
 > 362		memcpy_toio(to, buf, chunk);
   363		return len - chunk;
   364	}
   365	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH v3 1/4] iov_iter: Provide copy_iomem_to|from_iter()

[Michal Wajdeczko]

Define simple copy helpers that work on I/O memory. This will
allow reuse of existing framework functions in new use cases.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
---
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
---
v2: use iterate_and_advance to treat user_iter separately (Matthew)
v3: add explicit casts to make sparse happy (kernel test robot)
---
 include/linux/uio.h |  3 +++
 lib/iov_iter.c      | 66 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 853f9de5aa05..354a6b2d1e94 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -183,6 +183,9 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
 
+size_t copy_iomem_to_iter(const void __iomem *from, size_t bytes, struct iov_iter *i);
+size_t copy_iomem_from_iter(void __iomem *to, size_t bytes, struct iov_iter *i);
+
 static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
 		size_t bytes, struct iov_iter *i)
 {
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 908e75a28d90..a6eae4063366 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -323,6 +323,72 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 #endif
 
+static __always_inline
+size_t memcpy_iomem_to_iter(void *iter_to, size_t progress, size_t len,
+			    void *from, void *priv2)
+{
+	memcpy_fromio(iter_to, (const void __iomem *)from + progress, len);
+	return 0;
+}
+
+static __always_inline
+size_t memcpy_iomem_from_iter(void *iter_from, size_t progress, size_t len,
+			      void *to, void *priv2)
+{
+	memcpy_toio((void __iomem *)to + progress, iter_from, len);
+	return 0;
+}
+
+static __always_inline
+size_t copy_iomem_to_user_iter(void __user *iter_to, size_t progress,
+			       size_t len, void *from, void *priv2)
+{
+	unsigned char buf[SMP_CACHE_BYTES];
+	size_t chunk = min(len, sizeof(buf));
+
+	memcpy_fromio(buf, (const void __iomem *)from + progress, chunk);
+	chunk -= copy_to_user_iter(iter_to, progress, chunk, buf, priv2);
+	return len - chunk;
+}
+
+static __always_inline
+size_t copy_iomem_from_user_iter(void __user *iter_from, size_t progress,
+				 size_t len, void *to, void *priv2)
+{
+	unsigned char buf[SMP_CACHE_BYTES];
+	size_t chunk = min(len, sizeof(buf));
+
+	chunk -= copy_from_user_iter(iter_from, progress, chunk, buf, priv2);
+	memcpy_toio((void __iomem *)to, buf, chunk);
+	return len - chunk;
+}
+
+size_t copy_iomem_to_iter(const void __iomem *from, size_t bytes, struct iov_iter *i)
+{
+	if (WARN_ON_ONCE(i->data_source))
+		return 0;
+	if (user_backed_iter(i))
+		might_fault();
+
+	return iterate_and_advance(i, bytes, (void __force *)from,
+				   copy_iomem_to_user_iter,
+				   memcpy_iomem_to_iter);
+}
+EXPORT_SYMBOL(copy_iomem_to_iter);
+
+size_t copy_iomem_from_iter(void __iomem *to, size_t bytes, struct iov_iter *i)
+{
+	if (WARN_ON_ONCE(!i->data_source))
+		return 0;
+	if (user_backed_iter(i))
+		might_fault();
+
+	return iterate_and_advance(i, bytes, (void __force *)to,
+				   copy_iomem_from_user_iter,
+				   memcpy_iomem_from_iter);
+}
+EXPORT_SYMBOL(copy_iomem_from_iter);
+
 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 {
 	struct page *head;
-- 
2.43.0