[PATCH] drm/i915/gvt: always return zero if read pvinfo failed

[Zhenyu Wang]

On 2019.06.13 08:34:37 +0000, Li, Weinan Z wrote:
> > -----Original Message-----
> > From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> > Sent: Thursday, June 13, 2019 4:15 PM
> > To: Li, Weinan Z <weinan.z.li at intel.com>
> > Cc: intel-gvt-dev at lists.freedesktop.org
> > Subject: Re: [PATCH] drm/i915/gvt: always return zero if read pvinfo failed
> > 
> > On 2019.06.13 11:05:17 +0800, Weinan Li wrote:
> > > There is pvinfo reading come from vgpu might be failed, like reading
> > > from one unknown address, now GVT-g returns the vreg which is one
> > > uncertain value. To avoid misunderstanding, GVT-g will always return
> > > zero if reading failed occurred.
> > >
> > > Signed-off-by: Weinan Li <weinan.z.li at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/gvt/handlers.c | 7 +++++--
> > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gvt/handlers.c
> > > b/drivers/gpu/drm/i915/gvt/handlers.c
> > > index a6ade66349bd..eab657d65276 100644
> > > --- a/drivers/gpu/drm/i915/gvt/handlers.c
> > > +++ b/drivers/gpu/drm/i915/gvt/handlers.c
> > > @@ -1199,9 +1199,12 @@ static int pvinfo_mmio_read(struct intel_vgpu
> > *vgpu, unsigned int offset,
> > >  		invalid_read = true;
> > >  		break;
> > >  	}
> > > -	if (invalid_read)
> > > -		gvt_vgpu_err("invalid pvinfo read: [%x:%x] = %x\n",
> > > +	if (invalid_read) {
> > > +		gvt_vgpu_err("invalid pvinfo read: [0x%x:0x%x] = 0x0 instead of
> > > +0x%x\n",
> > >  				offset, bytes, *(u32 *)p_data);
> > > +		memset(p_data, 0, bytes);
> > > +	}
> > > +
> > 
> > Shouldn't we make sure to set zero for undefined pvinfo memory?
> > Instead of keep setting return value like this?
> > 
> There might be usage like this, write first then read back and check the return value.
> 

yeah, better we can follow like reserved bit definition, discard
write for undefined bits and return zero. 

-- 
Open Source Technology Center, Intel ltd.

$gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/intel-gvt-dev/attachments/20190613/d7bbfe2c/attachment.sig>