Hello,
I've just realized that part of the fix sent to avoid the race between
page promotion and resync contained a mistake.
This patch fixes it, and fixes also performance on 64bit guests by
resyncing on validation only when needed.
Like the previous patch, this should be applied to Xen-3.3 as well.
Thanks,
Gianluca
Signed-off-by: Gianluca Guida <gianluca.guida@xxxxxxxxxxxxx>
diff -r ab0c1bdede53 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c Wed Nov 26 11:14:26 2008 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c Thu Nov 27 19:00:50 2008 +0000
@@ -1886,13 +1886,6 @@ static shadow_l1e_t * shadow_get_and_cre
if ( r & SHADOW_SET_ERROR )
return NULL;
-#if (SHADOW_OPTIMIZATIONS && SHOPT_OUT_OF_SYNC )
- /* All pages walked are now pagetables. Safe to resync pages
- in case level 4 or 3 shadows were set. */
- if ( resync )
- shadow_resync_all(v, 0);
-#endif
-
/* This next line is important: in 32-on-PAE and 32-on-64 modes,
* the guest l1 table has an 8k shadow, and we need to return
* the right mfn of the pair. This call will set it for us as a
@@ -1900,6 +1893,14 @@ static shadow_l1e_t * shadow_get_and_cre
* compiled out.) */
(void) shadow_l1_index(sl1mfn, guest_l1_table_offset(gw->va));
}
+
+#if (SHADOW_OPTIMIZATIONS && SHOPT_OUT_OF_SYNC )
+ /* All pages walked are now pagetables. Safe to resync pages
+ in case level 4 or 3 shadows were set. */
+ if ( resync )
+ shadow_resync_all(v, 0);
+#endif
+
/* Now follow it down a level. Guaranteed to succeed. */
return sh_linear_l1_table(v) + shadow_l1_linear_offset(gw->va);
}
@@ -2176,7 +2177,8 @@ static int validate_gl4e(struct vcpu *v,
result |= SHADOW_SET_ERROR;
#if (SHADOW_OPTIMIZATIONS && SHOPT_OUT_OF_SYNC )
- shadow_resync_all(v, 0);
+ if ( mfn_valid(sl3mfn) )
+ shadow_resync_all(v, 0);
#endif
}
l4e_propagate_from_guest(v, new_gl4e, sl3mfn, &new_sl4e, ft_prefetch);
@@ -2232,7 +2234,8 @@ static int validate_gl3e(struct vcpu *v,
result |= SHADOW_SET_ERROR;
#if (SHADOW_OPTIMIZATIONS && SHOPT_OUT_OF_SYNC )
- shadow_resync_all(v, 0);
+ if ( mfn_valid(sl2mfn) )
+ shadow_resync_all(v, 0);
#endif
}
l3e_propagate_from_guest(v, new_gl3e, sl2mfn, &new_sl3e, ft_prefetch);
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