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Subject[patch 2/4] x86: PAT Change /dev/mem mmap with O_SYNC to use UC_MINUS
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>

---
arch/x86/mm/pat.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)

Index: tip/arch/x86/mm/pat.c
===================================================================
--- tip.orig/arch/x86/mm/pat.c 2008-08-20 14:25:18.000000000 -0700
+++ tip/arch/x86/mm/pat.c 2008-08-20 14:26:35.000000000 -0700
@@ -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
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
#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);
--



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