[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, 9 insertions, 0 deletions

diff --git a/mm/highmem.c b/mm/highmem.c
index 51e1c1995fec..be8f8d36a8b9 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -99,6 +99,15 @@ static void flush_all_zero_pkmaps(void)
         flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 }
 
+/* Flush all unused kmap mappings in order to remove stray
+   mappings. */
+void kmap_flush_unused(void)
+{
+        spin_lock(&kmap_lock);
+        flush_all_zero_pkmaps();
+        spin_unlock(&kmap_lock);
+}
+
 static inline unsigned long map_new_virtual(struct page *page)
 {
         unsigned long vaddr;