MM: Pass a PTE pointer to update_mmu_cache() rather than the PTE itself

On VIVT ARM, when we have multiple shared mappings of the same file
in the same MM, we need to ensure that we have coherency across all
copies.  We do this via make_coherent() by making the pages
uncacheable.

This used to work fine, until we allowed highmem with highpte - we
now have a page table which is mapped as required, and is not available
for modification via update_mmu_cache().

Ralf Beache suggested getting rid of the PTE value passed to
update_mmu_cache():

  On MIPS update_mmu_cache() calls __update_tlb() which walks pagetables
  to construct a pointer to the pte again.  Passing a pte_t * is much
  more elegant.  Maybe we might even replace the pte argument with the
  pte_t?

Ben Herrenschmidt would also like the pte pointer for PowerPC:

  Passing the ptep in there is exactly what I want.  I want that
  -instead- of the PTE value, because I have issue on some ppc cases,
  for I$/D$ coherency, where set_pte_at() may decide to mask out the
  _PAGE_EXEC.

So, pass in the mapped page table pointer into update_mmu_cache(), and
remove the PTE value, updating all implementations and call sites to
suit.

Includes a fix from Stephen Rothwell:

  sparc: fix fallout from update_mmu_cache API change

  Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 3 insertions, 2 deletions

diff --git a/arch/mn10300/include/asm/pgtable.h b/arch/mn10300/include/asm/pgtable.h
index 6dc30fc827c4..16d88577f3e0 100644
--- a/arch/mn10300/include/asm/pgtable.h
+++ b/arch/mn10300/include/asm/pgtable.h
@@ -466,7 +466,7 @@ static inline int set_kernel_exec(unsigned long vaddr, int enable)
  * the kernel page tables containing the necessary information by tlb-mn10300.S
  */
 extern void update_mmu_cache(struct vm_area_struct *vma,
-                             unsigned long address, pte_t pte);
+                             unsigned long address, pte_t *ptep);
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/mn10300/mm/mmu-context.c b/arch/mn10300/mm/mmu-context.c
index 31c9d27a75ae..36ba02191d40 100644
--- a/arch/mn10300/mm/mmu-context.c
+++ b/arch/mn10300/mm/mmu-context.c
@@ -51,9 +51,10 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
 /*
  * preemptively set a TLB entry
  */
-void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
+void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep)
 {
         unsigned long pteu, ptel, cnx, flags;
+        pte_t pte = *ptep;
 
         addr &= PAGE_MASK;
         ptel = pte_val(pte) & ~(xPTEL_UNUSED1 | xPTEL_UNUSED2);