On Fri, Mar 26, 2021 at 06:55:03AM +0100, Christoph Hellwig wrote:
Add a helper that calls remap_pfn_range for an struct io_mapping, relying on the pgprot pre-validation done when creating the mapping instead of doing it at runtime.
Signed-off-by: Christoph Hellwig hch@lst.de
include/linux/io-mapping.h | 3 +++ mm/Kconfig | 3 +++ mm/Makefile | 1 + mm/io-mapping.c | 29 +++++++++++++++++++++++++++++ 4 files changed, 36 insertions(+) create mode 100644 mm/io-mapping.c
diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h index c093e81310a9b3..e9743cfd858527 100644 --- a/include/linux/io-mapping.h +++ b/include/linux/io-mapping.h @@ -220,3 +220,6 @@ io_mapping_free(struct io_mapping *iomap) }
#endif /* _LINUX_IO_MAPPING_H */
+int io_mapping_map_user(struct io_mapping *iomap, struct vm_area_struct *vma,
unsigned long addr, unsigned long pfn, unsigned long size);
I'm not sure what exactly brought me to check this, but while debugging I noticed this outside the header guard. But then after some more checks I saw nothing actually selects CONFIG_IO_MAPPING because commit using it was reverted in commit 0e4fe0c9f2f9 ("Revert "i915: use io_mapping_map_user"")
Is this something we want to re-attempt moving to mm/ ?
thanks Lucas De Marchi
diff --git a/mm/Kconfig b/mm/Kconfig index 24c045b24b9506..6b0f2cfbfac0f3 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -872,4 +872,7 @@ config MAPPING_DIRTY_HELPERS config KMAP_LOCAL bool
+# struct io_mapping based helper. Selected by drivers that need them +config IO_MAPPING
- bool
endmenu diff --git a/mm/Makefile b/mm/Makefile index 72227b24a61688..c0135e385984bb 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -120,3 +120,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o obj-$(CONFIG_PTDUMP_CORE) += ptdump.o obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o +obj-$(CONFIG_IO_MAPPING) += io-mapping.o diff --git a/mm/io-mapping.c b/mm/io-mapping.c new file mode 100644 index 00000000000000..01b3627999304e --- /dev/null +++ b/mm/io-mapping.c @@ -0,0 +1,29 @@ +// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/mm.h> +#include <linux/io-mapping.h>
+/**
- io_mapping_map_user - remap an I/O mapping to userspace
- @iomap: the source io_mapping
- @vma: user vma to map to
- @addr: target user address to start at
- @pfn: physical address of kernel memory
- @size: size of map area
- Note: this is only safe if the mm semaphore is held when called.
- */
+int io_mapping_map_user(struct io_mapping *iomap, struct vm_area_struct *vma,
unsigned long addr, unsigned long pfn, unsigned long size)+{
- vm_flags_t expected_flags = VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
- if (WARN_ON_ONCE((vma->vm_flags & expected_flags) != expected_flags))
return -EINVAL;- /* We rely on prevalidation of the io-mapping to skip track_pfn(). */
- return remap_pfn_range_notrack(vma, addr, pfn, size,
__pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |(pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK)));+}
+EXPORT_SYMBOL_GPL(io_mapping_map_user);
2.30.1
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