uml: speed page fault path

Give the page fault code a specialized path.  There is only one page to look
at, so there's no point in going into the general page table walking code.
There's only going to be one host operation, so there are no opportunities for
merging.  So, we go straight to the pte we want, figure out what needs doing,
and do it.

While I was in here, I fixed the wart where the address passed to unmap was a
void *, but an unsigned long to map and protect.

This gives me just under 10% on a kernel build.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 67 insertions, 3 deletions

diff --git a/arch/um/kernel/skas/tlb.c b/arch/um/kernel/skas/tlb.c
index 304a5b0695a..c43901aa936 100644
--- a/arch/um/kernel/skas/tlb.c
+++ b/arch/um/kernel/skas/tlb.c
@@ -32,8 +32,7 @@ static int do_ops(union mm_context *mmu, struct host_vm_op *ops, int last,
 				  op->u.mmap.offset, finished, flush);
 			break;
 		case MUNMAP:
-			ret = unmap(&mmu->skas.id,
-				    (void *) op->u.munmap.addr,
+			ret = unmap(&mmu->skas.id, op->u.munmap.addr,
 				    op->u.munmap.len, finished, flush);
 			break;
 		case MPROTECT:
@@ -94,3 +93,66 @@ void force_flush_all_skas(void)
 	unsigned long end = proc_mm ? task_size : CONFIG_STUB_START;
         fix_range(current->mm, 0, end, 1);
 }
+
+void flush_tlb_page_skas(struct vm_area_struct *vma, unsigned long address)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	struct mm_struct *mm = vma->vm_mm;
+	void *flush = NULL;
+	int r, w, x, err = 0;
+	struct mm_id *mm_id;
+
+	pgd = pgd_offset(vma->vm_mm, address);
+	if(!pgd_present(*pgd))
+		goto kill;
+
+	pud = pud_offset(pgd, address);
+	if(!pud_present(*pud))
+		goto kill;
+
+	pmd = pmd_offset(pud, address);
+	if(!pmd_present(*pmd))
+		goto kill;
+
+	pte = pte_offset_kernel(pmd, address);
+
+	r = pte_read(*pte);
+	w = pte_write(*pte);
+	x = pte_exec(*pte);
+	if (!pte_young(*pte)) {
+		r = 0;
+		w = 0;
+	} else if (!pte_dirty(*pte)) {
+		w = 0;
+	}
+
+	mm_id = &mm->context.skas.id;
+	if(pte_newpage(*pte)){
+		if(pte_present(*pte)){
+			unsigned long long offset;
+			int fd;
+
+			fd = phys_mapping(pte_val(*pte) & PAGE_MASK, &offset);
+			err = map(mm_id, address, PAGE_SIZE, r, w, x, fd,
+				  offset, 1, &flush);
+		}
+		else err = unmap(mm_id, address, PAGE_SIZE, 1, &flush);
+	}
+	else if(pte_newprot(*pte))
+		err = protect(mm_id, address, PAGE_SIZE, r, w, x, 1, &flush);
+
+	if(err)
+		goto kill;
+
+	*pte = pte_mkuptodate(*pte);
+
+	return;
+
+kill:
+	printk("Failed to flush page for address 0x%lx\n", address);
+	force_sig(SIGKILL, current);
+}
+
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index e201ccf0ec8..00de86efcca 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -381,7 +381,9 @@ pte_t *addr_pte(struct task_struct *task, unsigned long addr)
 void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
 {
 	address &= PAGE_MASK;
-	flush_tlb_range(vma, address, address + PAGE_SIZE);
+
+	CHOOSE_MODE(flush_tlb_range(vma, address, address + PAGE_SIZE),
+		    flush_tlb_page_skas(vma, address));
 }
 
 void flush_tlb_all(void)