KVM: Call x86_decode_insn() only when needed

Move emulate_ctxt to kvm_vcpu to keep emulate context when we exit from kvm
module. Call x86_decode_insn() only when needed. Modify x86_emulate_insn() to
not modify the context if it must be re-entered.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 21 insertions, 3 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index c191093982d..dc9d2a870fb 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -913,10 +913,19 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
         unsigned long cr2 = ctxt->cr2;
         int no_wb = 0;
         u64 msr_data;
+        unsigned long saved_eip = 0;
         unsigned long _eflags = ctxt->eflags;
         struct decode_cache *c = &ctxt->decode;
         int rc = 0;
 
+        /* Shadow copy of register state. Committed on successful emulation.
+         * NOTE: we can copy them from vcpu as x86_decode_insn() doesn't
+         * modify them.
+         */
+
+        memcpy(c->regs, ctxt->vcpu->regs, sizeof c->regs);
+        saved_eip = c->eip;
+
         if ((c->d & ModRM) && (c->modrm_mod != 3))
                 cr2 = c->modrm_ea;
 
@@ -1250,7 +1259,11 @@ writeback:
         ctxt->vcpu->rip = c->eip;
 
 done:
-        return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
+        if (rc == X86EMUL_UNHANDLEABLE) {
+                c->eip = saved_eip;
+                return -1;
+        }
+        return 0;
 
 special_insn:
         if (c->twobyte)
@@ -1305,8 +1318,10 @@ push:
                                 register_address(ctxt->es_base,
                                                  c->regs[VCPU_REGS_RDI]),
                                 c->rep_prefix,
-                                c->regs[VCPU_REGS_RDX]) == 0)
+                                c->regs[VCPU_REGS_RDX]) == 0) {
+                        c->eip = saved_eip;
                         return -1;
+                }
                 return 0;
         case 0x6e:              /* outsb */
         case 0x6f:              /* outsw/outsd */
@@ -1321,8 +1336,10 @@ push:
                                                         ctxt->ds_base,
                                                  c->regs[VCPU_REGS_RSI]),
                                 c->rep_prefix,
-                                c->regs[VCPU_REGS_RDX]) == 0)
+                                c->regs[VCPU_REGS_RDX]) == 0) {
+                        c->eip = saved_eip;
                         return -1;
+                }
                 return 0;
         case 0x70 ... 0x7f: /* jcc (short) */ {
                 int rel = insn_fetch(s8, 1, c->eip);
@@ -1711,5 +1728,6 @@ twobyte_special_insn:
 
 cannot_emulate:
         DPRINTF("Cannot emulate %02x\n", c->b);
+        c->eip = saved_eip;
         return -1;
 }