linux/i386: relax highpte pinning/write-protecting

Signed-off-by: Jan Beulich <jbeulich@novell.com>

2 files changed, 25 insertions, 31 deletions

diff --git a/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c b/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
index ee7deae2a7..20838cce53 100644
--- a/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
+++ b/linux-2.6-xen-sparse/arch/i386/mm/highmem-xen.c
@@ -55,7 +55,9 @@ void *kmap_atomic(struct page *page, enum km_type type)
 /* Same as kmap_atomic but with PAGE_KERNEL_RO page protection. */
 void *kmap_atomic_pte(struct page *page, enum km_type type)
 {
-	return __kmap_atomic(page, type, PAGE_KERNEL_RO);
+	return __kmap_atomic(page, type,
+	                     test_bit(PG_pinned, &page->flags)
+	                     ? PAGE_KERNEL_RO : kmap_prot);
 }
 
 void kunmap_atomic(void *kvaddr, enum km_type type)
diff --git a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
index 2af24831ec..18f27c7cde 100644
--- a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
+++ b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
@@ -25,7 +25,6 @@
 #include <asm/mmu_context.h>
 
 #include <xen/features.h>
-#include <xen/foreign_page.h>
 #include <asm/hypervisor.h>
 
 static void pgd_test_and_unpin(pgd_t *pgd);
@@ -239,14 +238,6 @@ struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
 
 #ifdef CONFIG_HIGHPTE
 	pte = alloc_pages(GFP_KERNEL|__GFP_HIGHMEM|__GFP_REPEAT|__GFP_ZERO, 0);
-	if (pte && PageHighMem(pte)) {
-		struct mmuext_op op;
-
-		kmap_flush_unused();
-		op.cmd = MMUEXT_PIN_L1_TABLE;
-		op.arg1.mfn = pfn_to_mfn(page_to_pfn(pte));
-		BUG_ON(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
-	}
 #else
 	pte = alloc_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, 0);
 #endif
@@ -267,13 +258,8 @@ void pte_free(struct page *pte)
 		if (!pte_write(*virt_to_ptep(va)))
 			BUG_ON(HYPERVISOR_update_va_mapping(
 			       va, pfn_pte(pfn, PAGE_KERNEL), 0));
-	} else {
-		struct mmuext_op op;
-
-		op.cmd = MMUEXT_UNPIN_TABLE;
-		op.arg1.mfn = pfn_to_mfn(pfn);
-		BUG_ON(HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0);
-	}
+	} else
+		clear_bit(PG_pinned, &pte->flags);
 
 	ClearPageForeign(pte);
 	init_page_count(pte);
@@ -587,46 +573,48 @@ void make_pages_writable(void *va, unsigned int nr, unsigned int feature)
 	}
 }
 
-static inline void pgd_walk_set_prot(void *pt, pgprot_t flags)
+static inline int pgd_walk_set_prot(struct page *page, pgprot_t flags)
 {
-	struct page *page = virt_to_page(pt);
 	unsigned long pfn = page_to_pfn(page);
 
 	if (PageHighMem(page))
-		return;
+		return pgprot_val(flags) & _PAGE_RW
+		       ? test_and_clear_bit(PG_pinned, &page->flags)
+		       : !test_and_set_bit(PG_pinned, &page->flags);
+
 	BUG_ON(HYPERVISOR_update_va_mapping(
 		(unsigned long)__va(pfn << PAGE_SHIFT),
 		pfn_pte(pfn, flags), 0));
+
+	return 0;
 }
 
-static void pgd_walk(pgd_t *pgd_base, pgprot_t flags)
+static int pgd_walk(pgd_t *pgd_base, pgprot_t flags)
 {
 	pgd_t *pgd = pgd_base;
 	pud_t *pud;
 	pmd_t *pmd;
-	pte_t *pte;
-	int    g, u, m;
+	int    g, u, m, flush;
 
 	if (xen_feature(XENFEAT_auto_translated_physmap))
-		return;
+		return 0;
 
-	for (g = 0; g < USER_PTRS_PER_PGD; g++, pgd++) {
+	for (g = 0, flush = 0; g < USER_PTRS_PER_PGD; g++, pgd++) {
 		if (pgd_none(*pgd))
 			continue;
 		pud = pud_offset(pgd, 0);
 		if (PTRS_PER_PUD > 1) /* not folded */
-			pgd_walk_set_prot(pud,flags);
+			flush |= pgd_walk_set_prot(virt_to_page(pud),flags);
 		for (u = 0; u < PTRS_PER_PUD; u++, pud++) {
 			if (pud_none(*pud))
 				continue;
 			pmd = pmd_offset(pud, 0);
 			if (PTRS_PER_PMD > 1) /* not folded */
-				pgd_walk_set_prot(pmd,flags);
+				flush |= pgd_walk_set_prot(virt_to_page(pmd),flags);
 			for (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
 				if (pmd_none(*pmd))
 					continue;
-				pte = pte_offset_kernel(pmd,0);
-				pgd_walk_set_prot(pte,flags);
+				flush |= pgd_walk_set_prot(pmd_page(*pmd),flags);
 			}
 		}
 	}
@@ -635,11 +623,14 @@ static void pgd_walk(pgd_t *pgd_base, pgprot_t flags)
 		(unsigned long)pgd_base,
 		pfn_pte(virt_to_phys(pgd_base)>>PAGE_SHIFT, flags),
 		UVMF_TLB_FLUSH));
+
+	return flush;
 }
 
 static void __pgd_pin(pgd_t *pgd)
 {
-	pgd_walk(pgd, PAGE_KERNEL_RO);
+	if (pgd_walk(pgd, PAGE_KERNEL_RO))
+		kmap_flush_unused();
 	xen_pgd_pin(__pa(pgd));
 	set_bit(PG_pinned, &virt_to_page(pgd)->flags);
 }
@@ -647,7 +638,8 @@ static void __pgd_pin(pgd_t *pgd)
 static void __pgd_unpin(pgd_t *pgd)
 {
 	xen_pgd_unpin(__pa(pgd));
-	pgd_walk(pgd, PAGE_KERNEL);
+	if (pgd_walk(pgd, PAGE_KERNEL))
+		kmap_flush_unused();
 	clear_bit(PG_pinned, &virt_to_page(pgd)->flags);
 }