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, 44 insertions, 33 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 800ab5028ed3..710483669f34 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1251,45 +1251,56 @@ struct x86_emulate_ops emulate_ops = {
 int emulate_instruction(struct kvm_vcpu *vcpu,
                         struct kvm_run *run,
                         unsigned long cr2,
-                        u16 error_code)
+                        u16 error_code,
+                        int no_decode)
 {
-        struct x86_emulate_ctxt emulate_ctxt;
-        int r;
-        int cs_db, cs_l;
+        int r = 0;
 
         vcpu->mmio_fault_cr2 = cr2;
         kvm_x86_ops->cache_regs(vcpu);
 
-        kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
-
-        emulate_ctxt.vcpu = vcpu;
-        emulate_ctxt.eflags = kvm_x86_ops->get_rflags(vcpu);
-        emulate_ctxt.cr2 = cr2;
-        emulate_ctxt.mode = (emulate_ctxt.eflags & X86_EFLAGS_VM)
-                ? X86EMUL_MODE_REAL : cs_l
-                ? X86EMUL_MODE_PROT64 : cs_db
-                ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
-
-        if (emulate_ctxt.mode == X86EMUL_MODE_PROT64) {
-                emulate_ctxt.cs_base = 0;
-                emulate_ctxt.ds_base = 0;
-                emulate_ctxt.es_base = 0;
-                emulate_ctxt.ss_base = 0;
-        } else {
-                emulate_ctxt.cs_base = get_segment_base(vcpu, VCPU_SREG_CS);
-                emulate_ctxt.ds_base = get_segment_base(vcpu, VCPU_SREG_DS);
-                emulate_ctxt.es_base = get_segment_base(vcpu, VCPU_SREG_ES);
-                emulate_ctxt.ss_base = get_segment_base(vcpu, VCPU_SREG_SS);
-        }
-
-        emulate_ctxt.gs_base = get_segment_base(vcpu, VCPU_SREG_GS);
-        emulate_ctxt.fs_base = get_segment_base(vcpu, VCPU_SREG_FS);
-
         vcpu->mmio_is_write = 0;
         vcpu->pio.string = 0;
-        r = x86_decode_insn(&emulate_ctxt, &emulate_ops);
+
+        if (!no_decode) {
+                int cs_db, cs_l;
+                kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
+
+                vcpu->emulate_ctxt.vcpu = vcpu;
+                vcpu->emulate_ctxt.eflags = kvm_x86_ops->get_rflags(vcpu);
+                vcpu->emulate_ctxt.cr2 = cr2;
+                vcpu->emulate_ctxt.mode =
+                        (vcpu->emulate_ctxt.eflags & X86_EFLAGS_VM)
+                        ? X86EMUL_MODE_REAL : cs_l
+                        ? X86EMUL_MODE_PROT64 : cs_db
+                        ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
+
+                if (vcpu->emulate_ctxt.mode == X86EMUL_MODE_PROT64) {
+                        vcpu->emulate_ctxt.cs_base = 0;
+                        vcpu->emulate_ctxt.ds_base = 0;
+                        vcpu->emulate_ctxt.es_base = 0;
+                        vcpu->emulate_ctxt.ss_base = 0;
+                } else {
+                        vcpu->emulate_ctxt.cs_base =
+                                        get_segment_base(vcpu, VCPU_SREG_CS);
+                        vcpu->emulate_ctxt.ds_base =
+                                        get_segment_base(vcpu, VCPU_SREG_DS);
+                        vcpu->emulate_ctxt.es_base =
+                                        get_segment_base(vcpu, VCPU_SREG_ES);
+                        vcpu->emulate_ctxt.ss_base =
+                                        get_segment_base(vcpu, VCPU_SREG_SS);
+                }
+
+                vcpu->emulate_ctxt.gs_base =
+                                        get_segment_base(vcpu, VCPU_SREG_GS);
+                vcpu->emulate_ctxt.fs_base =
+                                        get_segment_base(vcpu, VCPU_SREG_FS);
+
+                r = x86_decode_insn(&vcpu->emulate_ctxt, &emulate_ops);
+        }
+
         if (r == 0)
-                r = x86_emulate_insn(&emulate_ctxt, &emulate_ops);
+                r = x86_emulate_insn(&vcpu->emulate_ctxt, &emulate_ops);
 
         if (vcpu->pio.string)
                 return EMULATE_DO_MMIO;
@@ -1313,7 +1324,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
         }
 
         kvm_x86_ops->decache_regs(vcpu);
-        kvm_x86_ops->set_rflags(vcpu, emulate_ctxt.eflags);
+        kvm_x86_ops->set_rflags(vcpu, vcpu->emulate_ctxt.eflags);
 
         if (vcpu->mmio_is_write) {
                 vcpu->mmio_needed = 0;
@@ -2055,7 +2066,7 @@ static int kvm_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                 vcpu->mmio_read_completed = 1;
                 vcpu->mmio_needed = 0;
                 r = emulate_instruction(vcpu, kvm_run,
-                                        vcpu->mmio_fault_cr2, 0);
+                                        vcpu->mmio_fault_cr2, 0, 1);
                 if (r == EMULATE_DO_MMIO) {
                         /*
                          * Read-modify-write.  Back to userspace.