[Xen-changelog] [xen-3.1-testing] x86, hvm: Flush local TLB after any change to linear pagetable

["Xen patchbot-3.1-testing" <patchbot-3.1-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxxxxxxxx>
# Date 1193761220 0
# Node ID 3ce0fb37cf590c9fc185d701691203ebd4feb296
# Parent  f983730bfc809f768506fbbb27b0c5a5ec3ea626
x86, hvm: Flush local TLB after any change to linear pagetable
mapping.

This was not needed when vmenter/vmexit always had the side effect of
flushing host TLBs.

But, with SVM ASIDs, it is possible to:
 (1) Update CR3 update,
 (2) vmenter the guest, and
 (3) and vmexit due to a page fault
all without an intervening host TLB flush.

Then the page fault code could use the linear pagetable
to read a top-level shadow page table entry.

But, without this change, it would fetch the wrong value
due to a stale TLB.

Signed-off-by: Robert Phillips <rphillips@xxxxxxxxxxxxxxx>
Signed-off-by: Ben Guthro <bguthro@xxxxxxxxxxxxxxx>
xen-unstable changeset:   16275:9379c83e14b5b0a9ab2fe627ed786a8abded0d38
xen-unstable date:        Tue Oct 30 16:15:17 2007 +0000
---
 xen/arch/x86/mm/shadow/multi.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+)

diff -r f983730bfc80 -r 3ce0fb37cf59 xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Thu Oct 25 09:46:36 2007 +0100
+++ b/xen/arch/x86/mm/shadow/multi.c    Tue Oct 30 16:20:20 2007 +0000
@@ -3351,6 +3351,21 @@ sh_update_linear_entries(struct vcpu *v)
 #else
 #error this should not happen
 #endif
+
+    if ( shadow_mode_external(d) )
+    {
+        /*
+         * Having modified the linear pagetable mapping, flush local host TLBs.
+         * This was not needed when vmenter/vmexit always had the side effect
+         * of flushing host TLBs but, with ASIDs, it is possible to finish 
+         * this CR3 update, vmenter the guest, vmexit due to a page fault, 
+         * without an intervening host TLB flush. Then the page fault code 
+         * could use the linear pagetable to read a top-level shadow page 
+         * table entry. But, without this change, it would fetch the wrong 
+         * value due to a stale TLB.
+         */
+        local_flush_tlb();
+    }
 }
 
 

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