linux-kernel - Re: [PATCH] vfio/platform: Fix reset

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Date:   Fri, 3 Mar 2023 13:41:14 +0000
From:   Mostafa Saleh <smostafa@...gle.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     eric.auger@...hat.com, cohuck@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfio/platform: Fix reset_required behaviour

On Fri, Mar 03, 2023 at 06:34:51AM -0700, Alex Williamson wrote:
> On Fri,  3 Mar 2023 12:11:52 +0000
> Mostafa Saleh <smostafa@...gle.com> wrote:
> 
> > vfio_platform_device has a flag reset_required that can be set from
> > module_param or vfio driver which indicates that reset is not a
> > requirement and it bypasses related checks.
> > 
> > This was introduced and implemented in vfio_platform_probe_common in
> > "b5add544d67 vfio, platform: make reset driver a requirement by default"
> > 
> > However, vfio_platform_probe_common was removed in
> > "ac1237912fb vfio/amba: Use the new device life cycle helpers"
> > 
> > And new implementation added in vfio_platform_init_common in
> > "5f6c7e0831a vfio/platform: Use the new device life cycle helpers"
> > 
> > which causes an error even if vfio-platform.reset_required=0, as it
> > only guards printing and not the return as before.
> > 
> > This patch fixes this by returning 0 if there is no reset function
> > for the device and reset_required=0. This is also consistent with
> > checks in vfio_platform_open_device and vfio_platform_close_device.
> > 
> > Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
> > ---
> >  drivers/vfio/platform/vfio_platform_common.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> > index 1a0a238ffa35..7325ff463cf0 100644
> > --- a/drivers/vfio/platform/vfio_platform_common.c
> > +++ b/drivers/vfio/platform/vfio_platform_common.c
> > @@ -650,10 +650,13 @@ int vfio_platform_init_common(struct vfio_platform_device *vdev)
> >  	mutex_init(&vdev->igate);
> >  
> >  	ret = vfio_platform_get_reset(vdev);
> > -	if (ret && vdev->reset_required)
> > +	if (ret && vdev->reset_required) {
> >  		dev_err(dev, "No reset function found for device %s\n",
> >  			vdev->name);
> > -	return ret;
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> >  }
> >  EXPORT_SYMBOL_GPL(vfio_platform_init_common);
> >  
> 
> An identical patch has already accepted and merged for v6.3:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=168a9c91fe0a1180959b6394f4566de7080244b6

Oh, sorry, missed that!

Thanks,
Mostafa