linux-kernel - Re: [PATCH 1/3] KVM: trace mmio read event properly

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Date:	Mon, 16 Jan 2012 12:18:15 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/3] KVM: trace mmio read event properly

On 01/16/2012 11:31 AM, Xiao Guangrong wrote:
> In current code, we use KVM_TRACE_MMIO_READ to trace mmio read event which
> only can be completed immediately, instead of it, we trace the time when
> read event occur, then cooperate with then later patch, we can know the time
> of mmio read emulation
>
> @@ -3744,6 +3740,8 @@ mmio:
>  	/*
>  	 * Is this MMIO handled locally?
>  	 */
> +	trace_kvm_mmio(write ? KVM_TRACE_MMIO_WRITE : KVM_TRACE_MMIO_READ,

It's better to push the conditional to the trace event itself, so it's
only evaluated if tracing is enabled.

> +			bytes, gpa, *(u64 *)val);

We get the wrong value for reads here, no?

Can't we leave the code as is, and infer the start of the event from the
last kvm_exit trace?

>  	handled = ops->read_write_mmio(vcpu, gpa, bytes, val);
>  	if (handled == bytes)
>  		return X86EMUL_CONTINUE;


-- 
error compiling committee.c: too many arguments to function

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