# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxxxx
# Node ID 2a99292b1a8aa74ca1abb90e2915f4adcb640eb8
# Parent a27f56a0ff43e9299a73b9979de68571ade25bf3
[XEN][PAE] Stores to PTEs in PAE mode use CMPXCHG to ensure atomicity.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
xen/arch/x86/mm.c | 78 +++++++++++++++++++++++++++++++++++-------------------
1 files changed, 51 insertions(+), 27 deletions(-)
diff -r a27f56a0ff43 -r 2a99292b1a8a xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Mon Jun 19 14:03:04 2006 +0100
+++ b/xen/arch/x86/mm.c Mon Jun 19 14:44:34 2006 +0100
@@ -108,11 +108,20 @@
#include <public/memory.h>
#ifdef VERBOSE
-#define MEM_LOG(_f, _a...) \
- printk("DOM%u: (file=mm.c, line=%d) " _f "\n", \
+#define MEM_LOG(_f, _a...) \
+ printk("DOM%u: (file=mm.c, line=%d) " _f "\n", \
current->domain->domain_id , __LINE__ , ## _a )
#else
#define MEM_LOG(_f, _a...) ((void)0)
+#endif
+
+/*
+ * PTE updates can be done with ordinary writes except:
+ * 1. Debug builds get extra checking by using CMPXCHG[8B].
+ * 2. PAE builds perform an atomic 8-byte store with CMPXCHG8B.
+ */
+#if !defined(NDEBUG) || defined(CONFIG_X86_PAE)
+#define PTE_UPDATE_WITH_CMPXCHG
#endif
/*
@@ -1173,16 +1182,27 @@ static inline int update_l1e(l1_pgentry_
intpte_t o = l1e_get_intpte(ol1e);
intpte_t n = l1e_get_intpte(nl1e);
- if ( unlikely(cmpxchg_user(pl1e, o, n) != 0) ||
- unlikely(o != l1e_get_intpte(ol1e)) )
- {
- MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte
- ": saw %" PRIpte,
- l1e_get_intpte(ol1e),
- l1e_get_intpte(nl1e),
- o);
- return 0;
- }
+ for ( ; ; )
+ {
+ if ( unlikely(cmpxchg_user(pl1e, o, n) != 0) )
+ {
+ MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte
+ ": saw %" PRIpte,
+ l1e_get_intpte(ol1e),
+ l1e_get_intpte(nl1e),
+ o);
+ return 0;
+ }
+
+ if ( o == l1e_get_intpte(ol1e) )
+ break;
+
+ /* Allowed to change in Accessed/Dirty flags only. */
+ BUG_ON((o ^ l1e_get_intpte(ol1e)) &
+ ~(int)(_PAGE_ACCESSED|_PAGE_DIRTY));
+ ol1e = l1e_from_intpte(o);
+ }
+
return 1;
#endif
}
@@ -1235,17 +1255,20 @@ static int mod_l1_entry(l1_pgentry_t *pl
#ifndef PTE_UPDATE_WITH_CMPXCHG
#define UPDATE_ENTRY(_t,_p,_o,_n) ({ (*(_p) = (_n)); 1; })
#else
-#define UPDATE_ENTRY(_t,_p,_o,_n) ({ \
- intpte_t __o = cmpxchg((intpte_t *)(_p), \
- _t ## e_get_intpte(_o), \
- _t ## e_get_intpte(_n)); \
- if ( __o != _t ## e_get_intpte(_o) ) \
- MEM_LOG("Failed to update %" PRIpte " -> %" PRIpte \
- ": saw %" PRIpte "", \
- (_t ## e_get_intpte(_o)), \
- (_t ## e_get_intpte(_n)), \
- (__o)); \
- (__o == _t ## e_get_intpte(_o)); })
+#define UPDATE_ENTRY(_t,_p,_o,_n) ({ \
+ for ( ; ; ) \
+ { \
+ intpte_t __o = cmpxchg((intpte_t *)(_p), \
+ _t ## e_get_intpte(_o), \
+ _t ## e_get_intpte(_n)); \
+ if ( __o == _t ## e_get_intpte(_o) ) \
+ break; \
+ /* Allowed to change in Accessed/Dirty flags only. */ \
+ BUG_ON((__o ^ _t ## e_get_intpte(_o)) & \
+ ~(int)(_PAGE_ACCESSED|_PAGE_DIRTY)); \
+ _o = _t ## e_from_intpte(__o); \
+ } \
+ 1; })
#endif
/* Update the L2 entry at pl2e to new value nl2e. pl2e is within frame pfn. */
@@ -2494,7 +2517,7 @@ static int destroy_grant_pte_mapping(
}
/* Delete pagetable entry. */
- if ( unlikely(__put_user(0, (intpte_t *)va)))
+ if ( unlikely(!update_l1e((l1_pgentry_t *)va, ol1e, l1e_empty())) )
{
MEM_LOG("Cannot delete PTE entry at %p", va);
put_page_type(page);
@@ -2574,7 +2597,7 @@ static int destroy_grant_va_mapping(
}
/* Delete pagetable entry. */
- if ( unlikely(__put_user(0, &pl1e->l1)) )
+ if ( unlikely(!update_l1e(pl1e, ol1e, l1e_empty())) )
{
MEM_LOG("Cannot delete PTE entry at %p", (unsigned long *)pl1e);
return GNTST_general_error;
@@ -3424,8 +3447,9 @@ static int ptwr_emulated_update(
}
else
{
- ol1e = *pl1e;
- *pl1e = nl1e;
+ ol1e = *pl1e;
+ if ( !update_l1e(pl1e, ol1e, nl1e) )
+ BUG();
}
unmap_domain_page(pl1e);
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