Jeremy Fitzhardinge wrote:
Jeremy Fitzhardinge wrote:
Hm, I don't think this interface will work for Xen. In Xen, whenever a
pagetable page gets mapped, it must be mapped RO. map_pt_hook gets
called after the mapping has already been created, so its too late for Xen.
I was planning on adding kmap_atomic_pte() for use in pte_offset_map*(),
which would be wired through to paravirt_ops to allow Xen to make this a
RO mapping. Would this be sufficient for you to do your vmi thing?
Something like this (compiled, untested).
J
diff -r 972e84c265cf arch/i386/kernel/paravirt.c
--- a/arch/i386/kernel/paravirt.c Thu Mar 01 19:12:49 2007 -0800
+++ b/arch/i386/kernel/paravirt.c Thu Mar 01 19:38:42 2007 -0800
@@ -32,6 +32,7 @@
#include <asm/fixmap.h>
#include <asm/apic.h>
#include <asm/tlbflush.h>
+#include <asm/highmem.h>
/* nop stub */
void _paravirt_nop(void)
@@ -605,6 +606,8 @@ struct paravirt_ops paravirt_ops = {
.kpte_clear_flush = native_kpte_clear_flush,
+ .kmap_atomic_pte = native_kmap_atomic_pte,
+
#ifdef CONFIG_X86_PAE
.set_pte_atomic = native_set_pte_atomic,
.set_pte_present = native_set_pte_present,
diff -r 972e84c265cf arch/i386/mm/highmem.c
--- a/arch/i386/mm/highmem.c Thu Mar 01 19:12:49 2007 -0800
+++ b/arch/i386/mm/highmem.c Thu Mar 01 19:38:42 2007 -0800
@@ -26,7 +26,7 @@ void kunmap(struct page *page)
* However when holding an atomic kmap is is not legal to sleep, so atomic
* kmaps are appropriate for short, tight code paths only.
*/
-void *kmap_atomic(struct page *page, enum km_type type)
+void *_kmap_atomic(struct page *page, enum km_type type, pgprot_t prot)
{
enum fixed_addresses idx;
unsigned long vaddr;
@@ -41,9 +41,14 @@ void *kmap_atomic(struct page *page, enu
return page_address(page);
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
- set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
+ set_pte(kmap_pte-idx, mk_pte(page, prot));
return (void*) vaddr;
+}
+
+void *kmap_atomic(struct page *page, enum km_type type)
+{
+ return _kmap_atomic(page, type, kmap_prot);
}
Yeah, actually that does work, since you pass the km_type, we can use
that. But I would rather not respin this for 2.6.21; getting this 100%
right can be tricky, and we've already done a good deal of testing on
this patch the way it is. Do you have any objection to me creating a
patch for -mm tree that implements kmap_atomic_pte the way you have
described above and attaching it to the Xen patch series, but leaving
the current patch as is for now?
Thanks, (and thanks for the suggestion - I was a little worried about
how it would play with Xen when HIGHPTE support came around, but it
looks like it will work for both of us with just one paravirt-op).
Zach
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