parisc: flush pages through tmpalias space

The kernel has an 8M tmpailas space (originally designed for copying
and clearing pages but now only used for clearing).  The idea is
to place zeros into the cache above a physical page rather than into
the physical page and flush the cache, because often the zeros end up
being replaced quickly anyway.

We can also use the tmpalias space for flushing a page.  The difference
here is that we have to do tmpalias processing in the non access data and
instruction traps.  The principle is the same: as long as we know the physical
address and have a virtual address congruent to the real one, the flush will
be effective.

In order to use the tmpalias space, the icache miss path has to be enhanced to
check for the alias region to make the fic instruction effective.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>

arch/parisc/include/asm/cacheflush.h

@@ -26,8 +26,6 @@ void flush_user_dcache_range_asm(unsigned long, unsigned long);
 void flush_kernel_dcache_range_asm(unsigned long, unsigned long);
 void flush_kernel_dcache_page_asm(void *);
 void flush_kernel_icache_page(void *);
-void flush_user_dcache_page(unsigned long);
-void flush_user_icache_page(unsigned long);
 void flush_user_dcache_range(unsigned long, unsigned long);
 void flush_user_icache_range(unsigned long, unsigned long);
 
@@ -90,12 +88,15 @@ void flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned
 void flush_cache_range(struct vm_area_struct *vma,
 		unsigned long start, unsigned long end);
 
+/* defined in pacache.S exported in cache.c used by flush_anon_page */
+void flush_dcache_page_asm(unsigned long phys_addr, unsigned long vaddr);
+
 #define ARCH_HAS_FLUSH_ANON_PAGE
 static inline void
 flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
 {
 	if (PageAnon(page))
-		flush_user_dcache_page(vmaddr);
+		flush_dcache_page_asm(page_to_phys(page), vmaddr);
 }
 
 #define ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE

arch/parisc/kernel/cache.c

@@ -27,12 +27,17 @@
 #include <asm/pgalloc.h>
 #include <asm/processor.h>
 #include <asm/sections.h>
+#include <asm/shmparam.h>
 
 int split_tlb __read_mostly;
 int dcache_stride __read_mostly;
 int icache_stride __read_mostly;
 EXPORT_SYMBOL(dcache_stride);
 
+void flush_dcache_page_asm(unsigned long phys_addr, unsigned long vaddr);
+EXPORT_SYMBOL(flush_dcache_page_asm);
+void flush_icache_page_asm(unsigned long phys_addr, unsigned long vaddr);
+
 
 /* On some machines (e.g. ones with the Merced bus), there can be
  * only a single PxTLB broadcast at a time; this must be guaranteed
@@ -259,81 +264,13 @@ void disable_sr_hashing(void)
 		panic("SpaceID hashing is still on!\n");
 }
 
-/* Simple function to work out if we have an existing address translation
- * for a user space vma. */
-static inline int translation_exists(struct vm_area_struct *vma,
-				unsigned long addr, unsigned long pfn)
-{
-	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
-	pmd_t *pmd;
-	pte_t pte;
-
-	if(pgd_none(*pgd))
-		return 0;
-
-	pmd = pmd_offset(pgd, addr);
-	if(pmd_none(*pmd) || pmd_bad(*pmd))
-		return 0;
-
-	/* We cannot take the pte lock here: flush_cache_page is usually
-	 * called with pte lock already held.  Whereas flush_dcache_page
-	 * takes flush_dcache_mmap_lock, which is lower in the hierarchy:
-	 * the vma itself is secure, but the pte might come or go racily.
-	 */
-	pte = *pte_offset_map(pmd, addr);
-	/* But pte_unmap() does nothing on this architecture */
-
-	/* Filter out coincidental file entries and swap entries */
-	if (!(pte_val(pte) & (_PAGE_FLUSH|_PAGE_PRESENT)))
-		return 0;
-
-	return pte_pfn(pte) == pfn;
-}
-
-/* Private function to flush a page from the cache of a non-current
- * process.  cr25 contains the Page Directory of the current user
- * process; we're going to hijack both it and the user space %sr3 to
- * temporarily make the non-current process current.  We have to do
- * this because cache flushing may cause a non-access tlb miss which
- * the handlers have to fill in from the pgd of the non-current
- * process. */
 static inline void
-flush_user_cache_page_non_current(struct vm_area_struct *vma,
-				  unsigned long vmaddr)
+__flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr,
+		   unsigned long physaddr)
 {
-	/* save the current process space and pgd */
-	unsigned long space = mfsp(3), pgd = mfctl(25);
-
-	/* we don't mind taking interrupts since they may not
-	 * do anything with user space, but we can't
-	 * be preempted here */
-	preempt_disable();
-
-	/* make us current */
-	mtctl(__pa(vma->vm_mm->pgd), 25);
-	mtsp(vma->vm_mm->context, 3);
-
-	flush_user_dcache_page(vmaddr);
-	if(vma->vm_flags & VM_EXEC)
-		flush_user_icache_page(vmaddr);
-
-	/* put the old current process back */
-	mtsp(space, 3);
-	mtctl(pgd, 25);
-	preempt_enable();
-}
-
-
-static inline void
-__flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr)
-{
-	if (likely(vma->vm_mm->context == mfsp(3))) {
-		flush_user_dcache_page(vmaddr);
-		if (vma->vm_flags & VM_EXEC)
-			flush_user_icache_page(vmaddr);
-	} else {
-		flush_user_cache_page_non_current(vma, vmaddr);
-	}
+	flush_dcache_page_asm(physaddr, vmaddr);
+	if (vma->vm_flags & VM_EXEC)
+		flush_icache_page_asm(physaddr, vmaddr);
 }
 
 void flush_dcache_page(struct page *page)
@@ -342,10 +279,8 @@ void flush_dcache_page(struct page *page)
 	struct vm_area_struct *mpnt;
 	struct prio_tree_iter iter;
 	unsigned long offset;
-	unsigned long addr;
+	unsigned long addr, old_addr = 0;
 	pgoff_t pgoff;
-	unsigned long pfn = page_to_pfn(page);
-
 
 	if (mapping && !mapping_mapped(mapping)) {
 		set_bit(PG_dcache_dirty, &page->flags);
@@ -369,20 +304,11 @@ void flush_dcache_page(struct page *page)
 		offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 		addr = mpnt->vm_start + offset;
 
-		/* Flush instructions produce non access tlb misses.
-		 * On PA, we nullify these instructions rather than
-		 * taking a page fault if the pte doesn't exist.
-		 * This is just for speed.  If the page translation
-		 * isn't there, there's no point exciting the
-		 * nadtlb handler into a nullification frenzy.
-		 *
-		 * Make sure we really have this page: the private
-		 * mappings may cover this area but have COW'd this
-		 * particular page.
-		 */
-  		if (translation_exists(mpnt, addr, pfn)) {
-			__flush_cache_page(mpnt, addr);
-			break;
+		if (old_addr == 0 || (old_addr & (SHMLBA - 1)) != (addr & (SHMLBA - 1))) {
+			__flush_cache_page(mpnt, addr, page_to_phys(page));
+			if (old_addr)
+				printk(KERN_ERR "INEQUIVALENT ALIASES 0x%lx and 0x%lx in file %s\n", old_addr, addr, mpnt->vm_file ? mpnt->vm_file->f_path.dentry->d_name.name : "(null)");
+			old_addr = addr;
 		}
 	}
 	flush_dcache_mmap_unlock(mapping);
@@ -573,7 +499,6 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long
 {
 	BUG_ON(!vma->vm_mm->context);
 
-	if (likely(translation_exists(vma, vmaddr, pfn)))
-		__flush_cache_page(vma, vmaddr);
+	__flush_cache_page(vma, vmaddr, page_to_phys(pfn_to_page(pfn)));
 
 }