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

[Avi Kivity <avi@redhat.com>]

  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:

> 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