[PATCHv2 1/3] KVM: x86 emulator: Rename variable that shadows another local variable.

[PATCHv2 1/3] KVM: x86 emulator: Rename variable that shadows another local variable.

[Gleb Natapov]

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
 arch/x86/kvm/emulate.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4a89348..8a77c99 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3424,7 +3424,7 @@ writeback:
 				&c->dst);
 
 	if (c->rep_prefix && (c->d & String)) {
-		struct read_cache *rc = &ctxt->decode.io_read;
+		struct read_cache *r = &ctxt->decode.io_read;
 		register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
 		/* The second termination condition only applies for REPE
 		 * and REPNE. Test if the repeat string operation prefix is
@@ -3444,8 +3444,8 @@ writeback:
 		 * Re-enter guest when pio read ahead buffer is empty or,
 		 * if it is not used, after each 1024 iteration.
 		 */
-		else if ((rc->end == 0 && !(c->regs[VCPU_REGS_RCX] & 0x3ff)) ||
-			 (rc->end != 0 && rc->end == rc->pos)) {
+		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;
 		}
-- 
1.7.1

[PATCHv2 2/3] KVM: x86 emulator: move string instruction completion check into separate function

[Gleb Natapov]

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
 arch/x86/kvm/emulate.c |   37 ++++++++++++++++++++++++-------------
 1 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8a77c99..922f874 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2938,6 +2938,28 @@ done:
 	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
 }
 
+static bool string_insn_completed(struct x86_emulate_ctxt *ctxt)
+{
+	struct decode_cache *c = &ctxt->decode;
+
+	/* The second termination condition only applies for REPE
+	 * and REPNE. Test if the repeat string operation prefix is
+	 * REPE/REPZ or REPNE/REPNZ and if it's the case it tests the
+	 * corresponding termination condition according to:
+	 * 	- if REPE/REPZ and ZF = 0 then done
+	 * 	- if REPNE/REPNZ and ZF = 1 then done
+	 */
+	if (((c->b == 0xa6) || (c->b == 0xa7) ||
+	     (c->b == 0xae) || (c->b == 0xaf))
+	    && (((c->rep_prefix == REPE_PREFIX) &&
+		 ((ctxt->eflags & EFLG_ZF) == 0))
+		|| ((c->rep_prefix == REPNE_PREFIX) &&
+		    ((ctxt->eflags & EFLG_ZF) == EFLG_ZF))))
+		return true;
+
+	return false;
+}
+
 int
 x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 {
@@ -3426,19 +3448,8 @@ writeback:
 	if (c->rep_prefix && (c->d & String)) {
 		struct read_cache *r = &ctxt->decode.io_read;
 		register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
-		/* The second termination condition only applies for REPE
-		 * and REPNE. Test if the repeat string operation prefix is
-		 * REPE/REPZ or REPNE/REPNZ and if it's the case it tests the
-		 * corresponding termination condition according to:
-		 * 	- if REPE/REPZ and ZF = 0 then done
-		 * 	- if REPNE/REPNZ and ZF = 1 then done
-		 */
-		if (((c->b == 0xa6) || (c->b == 0xa7) ||
-		     (c->b == 0xae) || (c->b == 0xaf))
-		    && (((c->rep_prefix == REPE_PREFIX) &&
-			 ((ctxt->eflags & EFLG_ZF) == 0))
-			|| ((c->rep_prefix == REPNE_PREFIX) &&
-			    ((ctxt->eflags & EFLG_ZF) == EFLG_ZF))))
+
+		if (string_insn_completed(ctxt))
 			ctxt->restart = false;
 		/*
 		 * Re-enter guest when pio read ahead buffer is empty or,
-- 
1.7.1

[PATCHv2 3/3] KVM: x86 emulator: get rid of "restart" in emulation context.

[Gleb Natapov]

x86_emulate_insn() will return 1 if instruction can be restarted
without re-entering a guest.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
 arch/x86/include/asm/kvm_emulate.h |    4 ++-
 arch/x86/kvm/emulate.c             |   43 ++++++++++++++++--------------------
 arch/x86/kvm/x86.c                 |   16 ++++++------
 3 files changed, 30 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index f22e5da..3a82ecd 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 */
@@ -251,6 +250,9 @@ struct x86_emulate_ctxt {
 #endif
 
 int x86_decode_insn(struct x86_emulate_ctxt *ctxt);
+#define EMULATION_FAILED -1
+#define EMULATION_OK 0
+#define EMULATION_RESTART 1
 int x86_emulate_insn(struct x86_emulate_ctxt *ctxt);
 int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
 			 u16 tss_selector, int reason,
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 922f874..a4cf1f6 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)
@@ -2635,9 +2634,6 @@ 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);
@@ -2990,10 +2986,8 @@ 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 */
 		if (address_mask(c, c->regs[VCPU_REGS_RCX]) == 0) {
-			ctxt->restart = false;
 			ctxt->eip = c->eip;
 			goto done;
 		}
@@ -3449,28 +3443,29 @@ writeback:
 		struct read_cache *r = &ctxt->decode.io_read;
 		register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
 
-		if (string_insn_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_insn_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 EMULATION_RESTART;
+			}
+			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;
+	return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
 
 twobyte_insn:
 	switch (c->b) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 524bd3f..112213e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4171,18 +4171,17 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 restart:
 	r = x86_emulate_insn(&vcpu->arch.emulate_ctxt);
 
-	if (r) { /* emulation failed */
+	if (r == 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;
@@ -4190,8 +4189,10 @@ restart:
 		if (vcpu->mmio_is_write)
 			vcpu->mmio_needed = 0;
 		r = EMULATE_DO_MMIO;
-	} else if (vcpu->arch.emulate_ctxt.restart)
+	} else if (r == EMULATION_RESTART)
 		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);
@@ -5090,8 +5091,7 @@ 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

Re: [PATCHv2 3/3] KVM: x86 emulator: get rid of "restart" in emulation context.

[Avi Kivity]

  On 08/25/2010 12:47 PM, Gleb Natapov wrote:
> x86_emulate_insn() will return 1 if instruction can be restarted
> without re-entering a guest.

Looks good.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

Re: [PATCHv2 1/3] KVM: x86 emulator: Rename variable that shadows another local variable.

[Marcelo Tosatti]

On Wed, Aug 25, 2010 at 12:47:41PM +0300, Gleb Natapov wrote:
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> ---
>  arch/x86/kvm/emulate.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)

Applied all, thanks.