Re: [PATCH 1/2] KVM: x86 emulator: don't update vcpu state if instruction is restarted.

[Gleb Natapov <gleb@redhat.com>]

On Sun, Aug 01, 2010 at 11:54:38AM +0300, Avi Kivity wrote:
>  On 08/01/2010 11:28 AM, Gleb Natapov wrote:
> >On Sat, Jul 31, 2010 at 08:25:13PM +0300, Avi Kivity wrote:
> >>  On 07/29/2010 03:11 PM, Gleb Natapov wrote:
> >>>No need to update vcpu state since instruction is in the middle of the
> >>>emulation.
> >>>
> >>>Signed-off-by: Gleb Natapov<gleb@redhat.com>
> >>>---
> >>>  arch/x86/kvm/x86.c |   31 +++++++++++++------------------
> >>>  1 files changed, 13 insertions(+), 18 deletions(-)
> >>>
> >>>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >>>index 76fbc32..7e5f075 100644
> >>>--- a/arch/x86/kvm/x86.c
> >>>+++ b/arch/x86/kvm/x86.c
> >>>@@ -4057,32 +4057,27 @@ restart:
> >>>  		return handle_emulation_failure(vcpu);
> >>>  	}
> >>>
> >>>-	toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
> >>>-	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
> >>>-	memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
> >>>-	kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
> >>>+	r = EMULATE_DONE;
> >>>
> >>>-	if (vcpu->arch.emulate_ctxt.exception>= 0) {
> >>>+	if (vcpu->arch.emulate_ctxt.exception>= 0)
> >>>  		inject_emulated_exception(vcpu);
> >>>-		return EMULATE_DONE;
> >>>-	}
> >>>-
> >>>-	if (vcpu->arch.pio.count) {
> >>>+	else if (vcpu->arch.pio.count) {
> >>>  		if (!vcpu->arch.pio.in)
> >>>  			vcpu->arch.pio.count = 0;
> >>>-		return EMULATE_DO_MMIO;
> >>>-	}
> >>>-
> >>>-	if (vcpu->mmio_needed) {
> >>>+		r = EMULATE_DO_MMIO;
> >>>+	} else if (vcpu->mmio_needed) {
> >>>  		if (vcpu->mmio_is_write)
> >>>  			vcpu->mmio_needed = 0;
> >>>-		return EMULATE_DO_MMIO;
> >>>-	}
> >>>-
> >>>-	if (vcpu->arch.emulate_ctxt.restart)
> >>>+		r = EMULATE_DO_MMIO;
> >>>+	} else if (vcpu->arch.emulate_ctxt.restart)
> >>>  		goto restart;
> >>>
> >>>-	return EMULATE_DONE;
> >>>+	toggle_interruptibility(vcpu, vcpu->arch.emulate_ctxt.interruptibility);
> >>>+	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
> >>>+	memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
> >>>+	kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
> >>>+
> >>>+	return r;
> >>>  }
> >>>  EXPORT_SYMBOL_GPL(emulate_instruction);
> >>>
> >>What about kvm-tpr-opt.c?  It uses rip after pio.
> >>
> >It uses rip _during_ pio. And pio emulation changes rip
> >only at the end of emulation.
> 
> But non-emulated pio does a skip_emulated_instruction() immediately
> (or so the code in kvm-tpr-opt.c assumes:
> 
Indeed, this is bug in non-emulated pio. But the patch does not change
rip behaviour for emulated pio. vcpu->arch.emulate_ctxt.eip is updated
only at the end of emulation.

> >static void vtpr_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> >{
> >    CPUState *env = cpu_single_env;
> >    uint32_t rip;
> >
> >    cpu_synchronize_state(env);
> >
> >    rip = env->eip - 2;
> >    write_byte_virt(env, rip, 0x66);
> >    write_byte_virt(env, rip + 1, 0x90);
> 
> )
> 
> -- 
> error compiling committee.c: too many arguments to function

--
			Gleb.