[PATCH] i386: PARAVIRT: add kmap_atomic_pte for mapping highpte pages

Xen and VMI both have special requirements when mapping a highmem pte
page into the kernel address space.  These can be dealt with by adding
a new kmap_atomic_pte() function for mapping highptes, and hooking it
into the paravirt_ops infrastructure.

Xen specifically wants to map the pte page RO, so this patch exposes a
helper function, kmap_atomic_prot, which maps the page with the
specified page protections.

This also adds a kmap_flush_unused() function to clear out the cached
kmap mappings.  Xen needs this to clear out any potential stray RW
mappings of pages which will become part of a pagetable.

[ Zach - vmi.c will need some attention after this patch.  It wasn't
  immediately obvious to me what needs to be done. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 10f44af76b4..5048b41428f 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -16,7 +16,9 @@
 #ifndef __ASSEMBLY__
 #include <linux/types.h>
 #include <linux/cpumask.h>
+#include <asm/kmap_types.h>
 
+struct page;
 struct thread_struct;
 struct Xgt_desc_struct;
 struct tss_struct;
@@ -187,6 +189,10 @@ struct paravirt_ops
 
         pte_t (*ptep_get_and_clear)(pte_t *ptep);
 
+#ifdef CONFIG_HIGHPTE
+        void *(*kmap_atomic_pte)(struct page *page, enum km_type type);
+#endif
+
 #ifdef CONFIG_X86_PAE
         void (*set_pte_atomic)(pte_t *ptep, pte_t pteval);
         void (*set_pte_present)(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte);
@@ -884,6 +890,15 @@ static inline void paravirt_release_pd(unsigned pfn)
         PVOP_VCALL1(release_pd, pfn);
 }
 
+#ifdef CONFIG_HIGHPTE
+static inline void *kmap_atomic_pte(struct page *page, enum km_type type)
+{
+        unsigned long ret;
+        ret = PVOP_CALL2(unsigned long, kmap_atomic_pte, page, type);
+        return (void *)ret;
+}
+#endif
+
 static inline void pte_update(struct mm_struct *mm, unsigned long addr,
                               pte_t *ptep)
 {