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Commit 1745cbc5 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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mm: Add vm_insert_pfn_prot() 



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: default avatarAndy Lutomirski <luto@kernel.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarAndrew 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: default avatarIngo Molnar <mingo@kernel.org>
parent f872f540

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

mm/memory.c

+23 −2
Original line number Diff line number Diff line
@@ -1563,9 +1563,30 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, 
 */

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)