On Wed, Mar 28, 2007 at 06:46:40AM +1000, Herbert Xu wrote:
>
> I've checked again and the accessed bit is certainly present on ppc
> as well as ia64. The only I don't know is if it's present on the
> nested page tables on ia64 but I see no reasons why it wouldn't be.
Here is a completely untested patch that demonstrates how this could
be done on x86.
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
diff -r 3ac19fda0bc2 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Fri Mar 02 12:11:52 2007 +0000
+++ b/xen/arch/x86/mm.c Wed Mar 28 22:58:45 2007 +1000
@@ -1262,6 +1262,36 @@ static void free_l4_table(struct page_in
#endif
+static inline int cmpxchg_intpte(intpte_t *p,
+ intpte_t *old,
+ intpte_t new,
+ unsigned long mfn,
+ struct vcpu *v)
+{
+ int rv;
+
+ for ( ; ; )
+ {
+ intpte_t t = *old;
+
+ rv = paging_cmpxchg_guest_entry(v, p, old, new, _mfn(mfn));
+ if ( unlikely(rv == 0) )
+ {
+ MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte
+ ": saw %" PRIpte, t, new, t);
+ break;
+ }
+
+ if ( t == *old )
+ break;
+
+ /* Allowed to change in Accessed/Dirty flags only. */
+ BUG_ON((t ^ *old) & ~(intpte_t)(_PAGE_ACCESSED|_PAGE_DIRTY));
+ }
+
+ return rv;
+}
+
/* How to write an entry to the guest pagetables.
* Returns 0 for failure (pointer not valid), 1 for success. */
static inline int update_intpte(intpte_t *p,
@@ -1274,27 +1304,7 @@ static inline int update_intpte(intpte_t
#ifndef PTE_UPDATE_WITH_CMPXCHG
rv = paging_write_guest_entry(v, p, new, _mfn(mfn));
#else
- {
- intpte_t t = old;
- for ( ; ; )
- {
- rv = paging_cmpxchg_guest_entry(v, p, &t, new, _mfn(mfn));
- if ( unlikely(rv == 0) )
- {
- MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte
- ": saw %" PRIpte, old, new, t);
- break;
- }
-
- if ( t == old )
- break;
-
- /* Allowed to change in Accessed/Dirty flags only. */
- BUG_ON((t ^ old) & ~(intpte_t)(_PAGE_ACCESSED|_PAGE_DIRTY));
-
- old = t;
- }
- }
+ rv = cmpxchg_intpte(p, &old, new, mfn, v);
#endif
return rv;
}
@@ -2598,6 +2608,7 @@ static int destroy_grant_va_mapping(
unsigned long addr, unsigned long frame, struct vcpu *v)
{
l1_pgentry_t *pl1e, ol1e;
+ intpte_t *ptep, opte, npte;
unsigned long gl1mfn;
int rc = 0;
@@ -2619,12 +2630,19 @@ static int destroy_grant_va_mapping(
}
/* Delete pagetable entry. */
- if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, l1e_empty(), gl1mfn, v)) )
+ ptep = (intpte_t *)pl1e;
+ opte = l1e_get_intpte(ol1e);
+ npte = l1e_get_intpte(l1e_empty());
+
+ if ( unlikely(!cmpxchg_intpte(ptep, opte, npte, mfn, v)) )
{
MEM_LOG("Cannot delete PTE entry at %p", (unsigned long *)pl1e);
rc = GNTST_general_error;
goto out;
}
+
+ if (!(opte & (intpte_t)_PAGE_ACCESSED))
+ rc = GNTST_unused;
out:
guest_unmap_l1e(v, pl1e);
diff -r 3ac19fda0bc2 xen/common/grant_table.c
--- a/xen/common/grant_table.c Fri Mar 02 12:11:52 2007 +0000
+++ b/xen/common/grant_table.c Wed Mar 28 22:58:45 2007 +1000
@@ -394,7 +394,7 @@ gnttab_map_grant_ref(
return 0;
}
-static void
+static int
__gnttab_unmap_grant_ref(
struct gnttab_unmap_grant_ref *op)
{
@@ -416,7 +416,7 @@ __gnttab_unmap_grant_ref(
{
gdprintk(XENLOG_INFO, "Bad handle (%d).\n", op->handle);
op->status = GNTST_bad_handle;
- return;
+ return 0;
}
map = &maptrack_entry(ld->grant_table, op->handle);
@@ -425,7 +425,7 @@ __gnttab_unmap_grant_ref(
{
gdprintk(XENLOG_INFO, "Zero flags for handle (%d).\n", op->handle);
op->status = GNTST_bad_handle;
- return;
+ return 0;
}
dom = map->domid;
@@ -437,7 +437,7 @@ __gnttab_unmap_grant_ref(
/* This can happen when a grant is implicitly unmapped. */
gdprintk(XENLOG_INFO, "Could not find domain %d\n", dom);
domain_crash(ld); /* naughty... */
- return;
+ return 0;
}
TRACE_1D(TRC_MEM_PAGE_GRANT_UNMAP, dom);
@@ -511,9 +511,17 @@ __gnttab_unmap_grant_ref(
gnttab_clear_flag(_GTF_reading, &sha->flags);
unmap_out:
- op->status = rc;
spin_unlock(&rd->grant_table->lock);
rcu_unlock_domain(rd);
+
+ op->status = rc;
+
+ if (rc == GNTST_unused) {
+ op->status = GNTST_okay;
+ return 0;
+ }
+
+ return 1;
}
static long
@@ -521,23 +529,25 @@ gnttab_unmap_grant_ref(
XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t) uop, unsigned int count)
{
int i;
+ int used = 0;
+ int err = -EFAULT;
struct gnttab_unmap_grant_ref op;
for ( i = 0; i < count; i++ )
{
if ( unlikely(__copy_from_guest_offset(&op, uop, i, 1)) )
goto fault;
- __gnttab_unmap_grant_ref(&op);
+ used |= __gnttab_unmap_grant_ref(&op);
if ( unlikely(__copy_to_guest_offset(uop, i, &op, 1)) )
goto fault;
}
- flush_tlb_mask(current->domain->domain_dirty_cpumask);
- return 0;
+ err = 0;
fault:
- flush_tlb_mask(current->domain->domain_dirty_cpumask);
- return -EFAULT;
+ if (used)
+ flush_tlb_mask(current->domain->domain_dirty_cpumask);
+ return err;
}
int
diff -r 3ac19fda0bc2 xen/include/public/grant_table.h
--- a/xen/include/public/grant_table.h Fri Mar 02 12:11:52 2007 +0000
+++ b/xen/include/public/grant_table.h Wed Mar 28 22:58:45 2007 +1000
@@ -360,6 +360,7 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_query_siz
/*
* Values for error status returns. All errors are -ve.
*/
+#define GNTST_unused (1) /* Entry is unused (internal status). */
#define GNTST_okay (0) /* Normal return. */
#define GNTST_general_error (-1) /* General undefined error. */
#define GNTST_bad_domain (-2) /* Unrecognsed domain id. */
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