linux-kernel - Re: [PATCH] kvm: x86: Use DEFINE_DEBUGFS

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Date:   Tue, 17 Sep 2019 21:34:08 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Yi Wang <wang.yi59@....com.cn>, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        xue.zhihong@....com.cn, up2wing@...il.com, wang.liang82@....com.cn
Subject: Re: [PATCH] kvm: x86: Use DEFINE_DEBUGFS_ATTRIBUTE for debugfs files

On 17/09/19 20:12, Greg Kroah-Hartman wrote:
> On Tue, Sep 17, 2019 at 07:18:33PM +0200, Paolo Bonzini wrote:
>> On 22/07/19 09:33, Yi Wang wrote:
>>> We got these coccinelle warning:
>>> ./arch/x86/kvm/debugfs.c:23:0-23: WARNING: vcpu_timer_advance_ns_fops
>>> should be defined with DEFINE_DEBUGFS_ATTRIBUTE
>>> ./arch/x86/kvm/debugfs.c:32:0-23: WARNING: vcpu_tsc_offset_fops should
>>> be defined with DEFINE_DEBUGFS_ATTRIBUTE
>>> ./arch/x86/kvm/debugfs.c:41:0-23: WARNING: vcpu_tsc_scaling_fops should
>>> be defined with DEFINE_DEBUGFS_ATTRIBUTE
>>> ./arch/x86/kvm/debugfs.c:49:0-23: WARNING: vcpu_tsc_scaling_frac_fops
>>> should be defined with DEFINE_DEBUGFS_ATTRIBUTE
>>>
>>> Use DEFINE_DEBUGFS_ATTRIBUTE() rather than DEFINE_SIMPLE_ATTRIBUTE()
>>> to fix this.
>>>
>>> Signed-off-by: Yi Wang <wang.yi59@....com.cn>
>>
>> It sucks though that you have to use a function with "unsafe" in the name.
> 
> I agree, why make this change?
> 
>> Greg, is the patch doing the right thing?
> 
> I can't tell.  What coccinelle script generated this patch?

Seems to be scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci.

//# Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
//# imposes some significant overhead as compared to
//# DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().

Paolo

> thanks,
> 
> greg k-h
>