From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH] KVM: APIC: avoid instruction emulation for EOI writes
Date: Mon, 29 Aug 2011 10:23:43 +0300
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References: <625BA99ED14B2D499DC4E29D8138F15063045B0C0C@shsmsx502.ccr.corp.intel.com>
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Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	"Dong, Eddie" <eddie.dong@intel.com>,
	Marcelo Tosatti <mtosatti@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
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On 08/29/2011 09:09 AM, Tian, Kevin wrote:
>
>   static int handle_apic_access(struct kvm_vcpu *vcpu)
>   {
> +	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
> +	int access_type, offset;
> +
> +	access_type = (exit_qualification>>  12)&  0xf;
> +	offset = exit_qualification&  0xfff;
> +	/*
> +	 * Sane guest uses MOV instead of string operations to
> +	 * write EOI, with written value not cared. So make a
> +	 * short-circuit here by avoiding heavy instruction
> +	 * emulation.
> +	 */
> +	if ((access_type == 1)&&  (offset == APIC_EOI)) {

Please replace this 1 with a #define.

> +		kvm_lapic_set_eoi(vcpu);
> +		skip_emulated_instruction(vcpu);
> +		return 1;
> +	}
>   	return emulate_instruction(vcpu, 0) == EMULATE_DONE;
>   }
>
>

Looks good otherwise.

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