[Intel-gfx] [PATCH] drm/i915: Setting pch_id for HSW/BDW in virtual environment

[Zhang, Xiong Y]

> On Thu, Jun 15, 2017 at 11:11:45AM +0800, Xiong Zhang wrote:
> > In a IGD passthrough environment, the real ISA bridge may doesn't exist.
> > then pch_id couldn't be correctly gotten from ISA bridge, but pch_id is
> > used to identify LPT_H and LPT_LP. Currently i915 treat all LPT pch as
> > LPT_H,then errors occur when i915 runs on LPT_LP machines with igd
> > passthrough.
> >
> > This patch set pch_id for HSW/BDW according to IGD type and isn't fully
> > correct. But it solves such issue on HSW/BDW ult/ulx machines.
> > QA CI system is blocked by this issue for a long time, it's better that
> > we could merge it to unblock QA CI system.
> >
> > We know the root cause is in device model of virtual passthrough, and
> > will resolve it in the future with several parts cooperation in kernel,
> > qemu and xen.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99938
> >
> > Signed-off-by: Xiong Zhang <xiong.y.zhang at intel.com>
> 
> Looks ok to me, this is the assumption of the non-passthrough case
> anyway:
> Reviewed-by: Imre Deak <imre.deak at intel.com>
> 
> I noticed a few issues in the surrounding code: SPT/SPT_LP and
> CNP/CNP_LP have the same problem, although we don't need to distinguish
> between them atm. I think a cleaner way would be to adjust id and ext_id
> in the pass-through case in intel_detect_pch() upfront and set
> dev_priv->pch_type accordingly the same way as it's done in the
> non-passthrough case.
[Zhang, Xiong Y] Thanks for your suggestion.
pch_id in passthrough is guessed and isn't fully accurate,  so I don't add it to
SPT and CNP. Currently we are seeking acceptable method to pass pch id from
host to guest, once this decided, we will follow your suggestion.
> 
> Also, unrelated to the pass-through case, the HAS_PCH_CNP_LP() macro
> looks bogus, it checks only 8 bits of the PCI device ID instead of 9, so
> it'll be false on CNP_LP platforms (and true on SPT_LP).
[Zhang, Xiong Y] Please help fix it although HAS_PCH_CNP_LP() isn't used atm.
> 
> --Imre
> 
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c
> b/drivers/gpu/drm/i915/i915_drv.c
> > index 1f802de..2e664c5 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -135,6 +135,10 @@ static enum intel_pch intel_virt_detect_pch(struct
> drm_i915_private *dev_priv)
> >  		DRM_DEBUG_KMS("Assuming CouarPoint PCH\n");
> >  	} else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
> >  		ret = PCH_LPT;
> > +		if (IS_HSW_ULT(dev_priv) || IS_BDW_ULT(dev_priv))
> > +			dev_priv->pch_id = INTEL_PCH_LPT_LP_DEVICE_ID_TYPE;
> > +		else
> > +			dev_priv->pch_id = INTEL_PCH_LPT_DEVICE_ID_TYPE;
> >  		DRM_DEBUG_KMS("Assuming LynxPoint PCH\n");
> >  	} else if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) {
> >  		ret = PCH_SPT;
> > --
> > 2.7.4
> >
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