Tim Deegan
2010-Oct-01 10:54 UTC
[Xen-devel] [PATCH] x86 shadow: reset up-pointers on all l3s when l3s stop being pinnable
x86 shadow: reset up-pointers on all l3s when l3s stop being pinnable.
Walking the pinned-shadows list isn''t enough: there could be an
unpinned
(but still shadowed) l3 somewhere and if we later try to unshadow it
it''ll have an up-pointer of PAGE_LIST_NULL:PAGE_LIST_NULL.
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
diff -r 71f836615ea2 xen/arch/x86/mm/shadow/common.c
--- a/xen/arch/x86/mm/shadow/common.c Fri Sep 24 15:54:39 2010 +0100
+++ b/xen/arch/x86/mm/shadow/common.c Fri Oct 01 11:53:49 2010 +0100
@@ -2772,6 +2772,47 @@ sh_remove_all_shadows_and_parents(struct
* detect that it is not a pagetable) is correct, but very slow.
* It means extra emulated writes and slows down removal of mappings. */
}
+
+/**************************************************************************/
+
+/* Reset the up-pointers of every L3 shadow to 0.
+ * This is called when l3 shadows stop being pinnable, to clear out all
+ * the list-head bits so the up-pointer field is properly inititalised. */
+static int sh_clear_up_pointer(struct vcpu *v, mfn_t smfn, mfn_t unused)
+{
+ mfn_to_page(smfn)->up = 0;
+ return 0;
+}
+
+void sh_reset_l3_up_pointers(struct vcpu *v)
+{
+ static hash_callback_t callbacks[SH_type_unused] = {
+ NULL, /* none */
+ NULL, /* l1_32 */
+ NULL, /* fl1_32 */
+ NULL, /* l2_32 */
+ NULL, /* l1_pae */
+ NULL, /* fl1_pae */
+ NULL, /* l2_pae */
+ NULL, /* l2h_pae */
+ NULL, /* l1_64 */
+ NULL, /* fl1_64 */
+ NULL, /* l2_64 */
+ NULL, /* l2h_64 */
+#if CONFIG_PAGING_LEVELS >= 4
+ sh_clear_up_pointer, /* l3_64 */
+#else
+ NULL, /* l3_64 */
+#endif
+ NULL, /* l4_64 */
+ NULL, /* p2m */
+ NULL /* unused */
+ };
+ static unsigned int callback_mask = 1 << SH_type_l3_64_shadow;
+
+ hash_foreach(v, callback_mask, callbacks, _mfn(INVALID_MFN));
+}
+
/**************************************************************************/
diff -r 71f836615ea2 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c Fri Sep 24 15:54:39 2010 +0100
+++ b/xen/arch/x86/mm/shadow/multi.c Fri Oct 01 11:53:49 2010 +0100
@@ -1634,12 +1634,10 @@ sh_make_shadow(struct vcpu *v, mfn_t gmf
page_list_for_each_safe(sp, t,
&v->domain->arch.paging.shadow.pinned_shadows)
{
if ( sp->u.sh.type == SH_type_l3_64_shadow )
- {
sh_unpin(v, page_to_mfn(sp));
- sp->up = 0;
- }
}
v->domain->arch.paging.shadow.opt_flags &=
~SHOPT_LINUX_L3_TOPLEVEL;
+ sh_reset_l3_up_pointers(v);
}
}
#endif
diff -r 71f836615ea2 xen/arch/x86/mm/shadow/private.h
--- a/xen/arch/x86/mm/shadow/private.h Fri Sep 24 15:54:39 2010 +0100
+++ b/xen/arch/x86/mm/shadow/private.h Fri Oct 01 11:53:49 2010 +0100
@@ -475,6 +475,12 @@ mfn_t oos_snapshot_lookup(struct vcpu *v
#endif /* (SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC) */
+
+/* Reset the up-pointers of every L3 shadow to 0.
+ * This is called when l3 shadows stop being pinnable, to clear out all
+ * the list-head bits so the up-pointer field is properly inititalised. */
+void sh_reset_l3_up_pointers(struct vcpu *v);
+
/******************************************************************************
* Flags used in the return value of the shadow_set_lXe() functions...
*/
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