[PATCH] SVM: avoid VMSAVE in ctxt-switch-to

[Jan Beulich <jbeulich@xxxxxxxx>]

Of the state saved by the insn and reloaded by the corresponding VMLOAD
- TR, syscall, and sysenter state are invariant while having Xen's state
  loaded,
- FS, GS, and LDTR are not used by Xen and get suitably set in PV
  context switch code.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -984,7 +984,6 @@ static void svm_ctxt_switch_to(struct vc
 
     svm_restore_dr(v);
 
-    svm_vmsave_pa(per_cpu(host_vmcb, cpu));
     vmcb->cleanbits.raw = 0;
     svm_tsc_ratio_load(v);