Commit 28df82eb authored by venkatesh.pallipadi@intel.com's avatar venkatesh.pallipadi@intel.com Committed by Ingo Molnar
Browse files

devmem, 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: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c15238df

arch/x86/mm/pat.c

+5 −12
Original line number Diff line number Diff line
@@ -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);

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