| Message ID | 20210326055505.1424432-3-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/4] mm: add remap_pfn_range_notrack | expand |
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 > >_______________________________________________ >Intel-gfx mailing list >Intel-gfx@lists.freedesktop.org >https://lists.freedesktop.org/mailman/listinfo/intel-gfx >
On Wed, Oct 20, 2021 at 08:40:05AM -0700, Lucas De Marchi wrote: > 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/ ? Yes, it would be very good to unexport apply_to_page_range(), it's a terrible interface to expose.
On Wed, Oct 20, 2021 at 09:37:51PM +0200, Peter Zijlstra wrote: > > 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/ ? > > Yes, it would be very good to unexport apply_to_page_range(), it's a > terrible interface to expose. Yes. We need to get back to this rather sooner than later. I'm a little swamped unfortunately.
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); 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);
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