linux-kernel - Re: [PATCH 1/4] KVM: MMU: support disable/enable mmu audit dynamicly

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Date:	Sun, 29 Aug 2010 12:16:30 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/4] KVM: MMU: support disable/enable mmu audit dynamicly

  On 08/28/2010 03:00 PM, Xiao Guangrong wrote:
> Add the debugfs file named 'mmu-debug', we can disable/enable mmu audit by
> this file:
>
> enable:
> echo 1>  debugfs/kvm/mmu-debug
>
> disable:
> echo 0>  debugfs/kvm/mmu-debug


Better as a runtime rw module parameter perhaps?  At least it avoids the 
large debugfs callbacks.

Also, call it audit to preserve the name.


> This patch not change the logic
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@...fujitsu.com>
> ---
>   arch/x86/kvm/Kconfig       |    6 +
>   arch/x86/kvm/mmu.c         |  250 ++--------------------------------
>   arch/x86/kvm/mmu_debug.c   |  329 ++++++++++++++++++++++++++++++++++++++++++++

Please put the move to mmu_debug in a separate patch.

> +
> +static void mmu_debug_enable(void)
> +{
> +	int ret;
> +
> +	if (mmu_debug)
> +		return;
> +
> +	ret = register_trace_kvm_mmu_audit(kvm_mmu_audit, NULL);
> +	WARN_ON(ret);
> +
> +	mmu_debug = true;
> +}

Really neat use of tracepoints.

> diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
> index 3aab0f0..28a0e1f 100644
> --- a/arch/x86/kvm/mmutrace.h
> +++ b/arch/x86/kvm/mmutrace.h
> @@ -195,6 +195,25 @@ DEFINE_EVENT(kvm_mmu_page_class, kvm_mmu_prepare_zap_page,
>
>   	TP_ARGS(sp)
>   );
> +
> +TRACE_EVENT(
> +	kvm_mmu_audit,
> +	TP_PROTO(struct kvm_vcpu *vcpu, const char *msg),
> +	TP_ARGS(vcpu, msg),
> +
> +	TP_STRUCT__entry(
> +		__field(struct kvm_vcpu *, vcpu)
> +		__field(const char *, msg)
> +	),

enum instead of char *, maybe something in userspace can make use of this.

> +
> +	TP_fast_assign(
> +		__entry->vcpu = vcpu;
> +		__entry->msg = msg;
> +	),
> +
> +	TP_printk("%s", __entry->msg)

Here, of course, you can use print_symbolic() to preserve readability.


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

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