KVM: SVM: copy instruction bytes from VMCB

In case of a nested page fault or an intercepted #PF newer SVM
implementations provide a copy of the faulting instruction bytes
in the VMCB.
Use these bytes to feed the instruction emulator and avoid the costly
guest instruction fetch in this case.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 36534ecaf59..caf966781d2 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2610,7 +2610,7 @@ done:
 }
 
 int
-x86_decode_insn(struct x86_emulate_ctxt *ctxt)
+x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 {
         struct x86_emulate_ops *ops = ctxt->ops;
         struct decode_cache *c = &ctxt->decode;
@@ -2621,7 +2621,10 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt)
         struct operand memop = { .type = OP_NONE };
 
         c->eip = ctxt->eip;
-        c->fetch.start = c->fetch.end = c->eip;
+        c->fetch.start = c->eip;
+        c->fetch.end = c->fetch.start + insn_len;
+        if (insn_len > 0)
+                memcpy(c->fetch.data, insn, insn_len);
         ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS);
 
         switch (mode) {