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[Xen-devel] [PATCH v2 for-4.7 4/5] x86/svm: Don't unconditionally use a new ASID in svm_invlpg_intercept()

paging_invlpg() already returns a boolean indicating whether an invalidation
is necessary or not.  A return value of 0 indicates that the specified virtual
address wasn't shadowed (or has already been flushed), cannot currently be
cached in the TLB.

This is a performance optimisation.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>

While being a performance optimisation, the main purpose of splitting this
patch out is to separate the functional change.  The following patch performs
some function shuffling, and this patch makes the following one more obviously

 * Newly split out
 xen/arch/x86/hvm/svm/svm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 7634c3f..081a5d8 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2224,8 +2224,8 @@ static void svm_invlpg_intercept(unsigned long vaddr)
     struct vcpu *curr = current;
-    paging_invlpg(curr, vaddr);
-    svm_asid_g_invlpg(curr, vaddr);
+    if ( paging_invlpg(curr, vaddr) )
+        svm_asid_g_invlpg(curr, vaddr);
 static struct hvm_function_table __initdata svm_function_table = {

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