linux-kernel - Re: [PATCH 2/2] drm/i915/gvt: Avoid full proxy f_ops for vgpu

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Message-ID: <Y76JGj0cJpYr6/rv@intel.com>
Date:   Wed, 11 Jan 2023 05:02:02 -0500
From:   Rodrigo Vivi <rodrigo.vivi@...el.com>
To:     Deepak R Varma <drv@...lo.com>
CC:     Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        <dri-devel@...ts.freedesktop.org>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Zhi Wang <zhi.a.wang@...el.com>
Subject: Re: [PATCH 2/2] drm/i915/gvt: Avoid full proxy f_ops for vgpu_status
 debug attributes

On Tue, Jan 10, 2023 at 01:49:57PM -0500, Rodrigo Vivi wrote:
> On Wed, Jan 11, 2023 at 12:00:12AM +0530, Deepak R Varma wrote:
> > Using DEFINE_SIMPLE_ATTRIBUTE macro with the debugfs_create_file()
> > function adds the overhead of introducing a proxy file operation
> > functions to wrap the original read/write inside file removal protection
> > functions. This adds significant overhead in terms of introducing and
> > managing the proxy factory file operations structure and function
> > wrapping at runtime.
> > As a replacement, a combination of DEFINE_DEBUGFS_ATTRIBUTE macro paired
> > with debugfs_create_file_unsafe() is suggested to be used instead.  The
> > DEFINE_DEBUGFS_ATTRIBUTE utilises debugfs_file_get() and
> > debugfs_file_put() wrappers to protect the original read and write
> > function calls for the debug attributes. There is no need for any
> > runtime proxy file operations to be managed by the debugfs core.
> > Following coccicheck make command helped identify this change:
> > 
> > make coccicheck M=drivers/gpu/drm/i915/ MODE=patch COCCI=./scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
> > 
> > Signed-off-by: Deepak R Varma <drv@...lo.com>
> 
> I believe these 2 gvt cases could be done in one patch.
> But anyways,
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
> 
> for both patches... and will leave these 2 patches for gvt folks
> to apply. Unless they ack and I apply in the drm-intel along with the other ones.

Actually, could you please address the checkpatch issues before we can push?
Sorry about that, but just noticed now when I was going to push the other ones.

> 
> > ---
> >  drivers/gpu/drm/i915/gvt/debugfs.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gvt/debugfs.c b/drivers/gpu/drm/i915/gvt/debugfs.c
> > index 03f081c3d9a4..baccbf1761b7 100644
> > --- a/drivers/gpu/drm/i915/gvt/debugfs.c
> > +++ b/drivers/gpu/drm/i915/gvt/debugfs.c
> > @@ -165,7 +165,7 @@ static int vgpu_status_get(void *data, u64 *val)
> >  	return 0;
> >  }
> >  
> > -DEFINE_SIMPLE_ATTRIBUTE(vgpu_status_fops, vgpu_status_get, NULL, "0x%llx\n");
> > +DEFINE_DEBUGFS_ATTRIBUTE(vgpu_status_fops, vgpu_status_get, NULL, "0x%llx\n");
> >  
> >  /**
> >   * intel_gvt_debugfs_add_vgpu - register debugfs entries for a vGPU
> > @@ -182,8 +182,8 @@ void intel_gvt_debugfs_add_vgpu(struct intel_vgpu *vgpu)
> >  			    &vgpu_mmio_diff_fops);
> >  	debugfs_create_file_unsafe("scan_nonprivbb", 0644, vgpu->debugfs, vgpu,
> >  				   &vgpu_scan_nonprivbb_fops);
> > -	debugfs_create_file("status", 0644, vgpu->debugfs, vgpu,
> > -			    &vgpu_status_fops);
> > +	debugfs_create_file_unsafe("status", 0644, vgpu->debugfs, vgpu,
> > +				   &vgpu_status_fops);
> >  }
> >  
> >  /**
> > -- 
> > 2.34.1
> > 
> > 
> >