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

Avi Kivity
2010-08-29T09:16:34Z

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@cn.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