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mm: Add vm_insert_pfn_prot()

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The x86 vvar vma contains pages with differing cacheability
flags.  x86 currently implements this by manually inserting all
the ptes using (io_)remap_pfn_range when the vma is set up.

x86 wants to move to using .fault with VM_FAULT_NOPAGE to set up
the mappings as needed.  The correct API to use to insert a pfn
in .fault is vm_insert_pfn(), but vm_insert_pfn() can't override the
vma's cache mode, and the HPET page in particular needs to be
uncached despite the fact that the rest of the VMA is cached.

Add vm_insert_pfn_prot() to support varying cacheability within
the same non-COW VMA in a more sane manner.

x86 could alternatively use multiple VMAs, but that's messy,
would break CRIU, and would create unnecessary VMAs that would
waste memory.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d2938d1eb37be7a5e4f86182db646551f11e45aa.1451446564.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-12-29 20:12:20 -08:00 committed by Ingo Molnar
parent f872f5400c
commit 1745cbc5d0
2 changed files with 25 additions and 2 deletions
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2
include/linux/mm.h
View File

@ -2080,6 +2080,8 @@ int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn);
int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, pgprot_t pgprot);
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn);
int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);

25
mm/memory.c
View File

@ -1563,9 +1563,30 @@ out:
*/
int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn)
{
return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_insert_pfn);
/**
* vm_insert_pfn_prot - insert single pfn into user vma with specified pgprot
* @vma: user vma to map to
* @addr: target user address of this page
* @pfn: source kernel pfn
* @pgprot: pgprot flags for the inserted page
*
* This is exactly like vm_insert_pfn, except that it allows drivers to
* to override pgprot on a per-page basis.
*
* This only makes sense for IO mappings, and it makes no sense for
* cow mappings. In general, using multiple vmas is preferable;
* vm_insert_pfn_prot should only be used if using multiple VMAs is
* impractical.
*/
int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, pgprot_t pgprot)
{
int ret;
pgprot_t pgprot = vma->vm_page_prot;
/*
* Technically, architectures with pte_special can avoid all these
* restrictions (same for remap_pfn_range). However we would like
@ -1587,7 +1608,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
return ret;
}
EXPORT_SYMBOL(vm_insert_pfn);
EXPORT_SYMBOL(vm_insert_pfn_prot);
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn)