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devmem, x86: PAT Change /dev/mem mmap with O_SYNC to use UC_MINUS

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All kernel mappings like ioremap(), etc uses UC_MINUS as the type. /dev/mem
mappings with /dev/mem being opened with O_SYNC however was using UC,
resulting in a conflict with /dev/mem mmap failing. This seems to be
affecting some apps (one being flashrom) which are using O_SYNC and which were
working before.

Switch /dev/mem with O_SYNC also to UC_MINUS.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
venkatesh.pallipadi@intel.com 2008-08-20 16:45:52 -07:00 committed by Ingo Molnar
parent c15238df3b
commit 28df82ebab
1 changed files with 5 additions and 12 deletions
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17
arch/x86/mm/pat.c
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@ -390,14 +390,6 @@ int free_memtype(u64 start, u64 end)
}
/*
* /dev/mem mmap interface. The memtype used for mapping varies:
* - Use UC for mappings with O_SYNC flag
* - Without O_SYNC flag, if there is any conflict in reserve_memtype,
* inherit the memtype from existing mapping.
* - Else use UC_MINUS memtype (for backward compatibility with existing
* X drivers.
*/
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t vma_prot)
{
@ -435,14 +427,14 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t *vma_prot)
{
u64 offset = ((u64) pfn) << PAGE_SHIFT;
unsigned long flags = _PAGE_CACHE_UC_MINUS;
unsigned long flags = -1;
int retval;
if (!range_is_allowed(pfn, size))
return 0;
if (file->f_flags & O_SYNC) {
flags = _PAGE_CACHE_UC;
flags = _PAGE_CACHE_UC_MINUS;
}
#ifdef CONFIG_X86_32
@ -465,13 +457,14 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
#endif
/*
* With O_SYNC, we can only take UC mapping. Fail if we cannot.
* With O_SYNC, we can only take UC_MINUS mapping. Fail if we cannot.
*
* Without O_SYNC, we want to get
* - WB for WB-able memory and no other conflicting mappings
* - UC_MINUS for non-WB-able memory with no other conflicting mappings
* - Inherit from confliting mappings otherwise
*/
if (flags != _PAGE_CACHE_UC_MINUS) {
if (flags != -1) {
retval = reserve_memtype(offset, offset + size, flags, NULL);
} else {
retval = reserve_memtype(offset, offset + size, -1, &flags);