x86_emulate_insn() will return 1 if instruction can be restarted
without re-entering a guest.
Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_emulate.h | 1 -
arch/x86/kvm/emulate.c | 47 ++++++++++++++++-------------------
arch/x86/kvm/x86.c | 16 ++++++------
3 files changed, 30 insertions(+), 34 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index f22e5da..5e120a7 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -220,7 +220,6 @@ struct x86_emulate_ctxt {
/* interruptibility state, as a result of execution of STI or MOV SS */
int interruptibility;
- bool restart; /* restart string instruction after writeback */
bool perm_ok; /* do not check permissions if true */
int exception; /* exception that happens during emulation or -1 */
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d34d706..d98fc3b 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -438,7 +438,6 @@ static void emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
ctxt->exception = vec;
ctxt->error_code = error;
ctxt->error_code_valid = valid;
- ctxt->restart = false;
}
static void emulate_gp(struct x86_emulate_ctxt *ctxt, int err)
@@ -2618,9 +2617,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt)
struct opcode opcode, *g_mod012, *g_mod3;
struct operand memop = { .type = OP_NONE };
- /* we cannot decode insn before we complete previous rep insn */
- WARN_ON(ctxt->restart);
-
c->eip = ctxt->eip;
c->fetch.start = c->fetch.end = c->eip;
ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS);
@@ -2977,10 +2973,11 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
}
if (c->rep_prefix && (c->d & String)) {
- ctxt->restart = true;
- /* All REP prefixes have the same first termination condition */
+ /*
+ * counter == 0 termination condition is checked before
+ * instruction execution.
+ */
if (address_mask(c, c->regs[VCPU_REGS_RCX]) == 0) {
- ctxt->restart = false;
ctxt->eip = c->eip;
goto done;
}
@@ -3422,26 +3419,26 @@ writeback:
struct read_cache *r = &ctxt->decode.io_read;
register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
-
- if (string_inst_completed(ctxt))
- ctxt->restart = false;
- /*
- * Re-enter guest when pio read ahead buffer is empty or,
- * if it is not used, after each 1024 iteration.
- */
- else if ((r->end == 0 && !(c->regs[VCPU_REGS_RCX] & 0x3ff)) ||
- (r->end != 0 && r->end == r->pos)) {
- ctxt->restart = false;
- c->eip = ctxt->eip;
+ if (!string_inst_completed(ctxt)) {
+ /*
+ * Re-enter guest when pio read ahead buffer is empty
+ * or, if it is not used, after each 1024 iteration.
+ */
+ if ((r->end != 0 || c->regs[VCPU_REGS_RCX] & 0x3ff) &&
+ (r->end == 0 || r->end != r->pos)) {
+ /*
+ * Reset read cache. Usually happens before
+ * decode, but since instruction is restarted
+ * we have to do it here.
+ */
+ ctxt->decode.mem_read.end = 0;
+ return 1; /* restart instruction */
+ }
+ goto done; /* skip rip writeback */
}
}
- /*
- * reset read cache here in case string instruction is restared
- * without decoding
- */
- ctxt->decode.mem_read.end = 0;
- if (!ctxt->restart)
- ctxt->eip = c->eip;
+
+ ctxt->eip = c->eip;
done:
return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4e179c5..131f2c8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4066,18 +4066,17 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
restart:
r = x86_emulate_insn(&vcpu->arch.emulate_ctxt);
- if (r) { /* emulation failed */
+ if (r < 0) { /* emulation failed */
if (reexecute_instruction(vcpu, cr2))
return EMULATE_DONE;
return handle_emulation_failure(vcpu);
}
- r = EMULATE_DONE;
-
- if (vcpu->arch.emulate_ctxt.exception >= 0)
+ if (vcpu->arch.emulate_ctxt.exception >= 0) {
inject_emulated_exception(vcpu);
- else if (vcpu->arch.pio.count) {
+ r = EMULATE_DONE;
+ } else if (vcpu->arch.pio.count) {
if (!vcpu->arch.pio.in)
vcpu->arch.pio.count = 0;
r = EMULATE_DO_MMIO;
@@ -4085,8 +4084,10 @@ restart:
if (vcpu->mmio_is_write)
vcpu->mmio_needed = 0;
r = EMULATE_DO_MMIO;
- } else if (vcpu->arch.emulate_ctxt.restart)
+ } else if (r > 0)
goto restart;
+ else
+ r = EMULATE_DONE;
toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
@@ -4909,8 +4910,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
if (!irqchip_in_kernel(vcpu->kvm))
kvm_set_cr8(vcpu, kvm_run->cr8);
- if (vcpu->arch.pio.count || vcpu->mmio_needed ||
- vcpu->arch.emulate_ctxt.restart) {
+ if (vcpu->arch.pio.count || vcpu->mmio_needed) {
if (vcpu->mmio_needed) {
memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8);
vcpu->mmio_read_completed = 1;
--
1.7.1
--
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