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Date:   Tue, 17 Jan 2023 14:29:37 -0500
From:   Rodrigo Vivi <rodrigo.vivi@intel.com>
To:     Zhenyu Wang <zhenyuw@linux.intel.com>
CC:     Saurabh Singh Sengar <ssengar@microsoft.com>,
        <dri-devel@lists.freedesktop.org>, Deepak R Varma <drv@mailo.com>,
        <intel-gvt-dev@lists.freedesktop.org>,
        <intel-gfx@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        Praveen Kumar <kumarpraveen@linux.microsoft.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        "David Airlie" <airlied@gmail.com>
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/i915/gvt: Avoid full proxy f_ops for
 vgpu_status debug attributes
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On Mon, Jan 16, 2023 at 01:44:46PM +0800, Zhenyu Wang wrote:
> On 2023.01.10 13:49:57 -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@mailo.com>
> > 
> > I believe these 2 gvt cases could be done in one patch.
> > But anyways,
> > 
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.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.
> >
> 
> yeah, they're fine with me, feel free to apply them directly.
> 
> Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>

Unfortunately I got some conflicts when trying to apply on drm-intel-next.

We probably need a new version, and probably through gvt branches it
will be easier to handle conflicts if they appear.

> 
> thanks!
> 
> > > ---
> > >  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
> > > 
> > > 
> > >