[Intel-gfx] [PATCH] drm/i915: Detect virtual south bridge

[Tian, Kevin]

> From: Jesse Barnes [mailto:jbarnes at virtuousgeek.org]
> Sent: Friday, September 25, 2015 12:41 AM
> 
> On 08/28/2015 05:10 AM, robert.beckett at intel.com wrote:
> > From: Robert Beckett <robert.beckett at intel.com>
> >
> > Virtualized systems often use a virtual P2X4 south bridge.
> > Detect this in intel_detect_pch and make a best guess as to which PCH
> > we should be using.
> >
> > This was seen on vmware esxi hypervisor. When passing the graphics device
> > through to a guest, it can not pass through the PCH. Instead it simulates
> > a P2X4 southbridge.
> >
> > Signed-off-by: Robert Beckett <robert.beckett at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c |   30
> ++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/i915/i915_drv.h |    1 +
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index ce3bd0c..8e158b3 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -443,6 +443,34 @@ static const struct pci_device_id pciidlist[] = {		/* aka
> */
> >
> >  MODULE_DEVICE_TABLE(pci, pciidlist);
> >
> > +static enum intel_pch intel_virt_detect_pch(struct drm_device *dev)
> > +{
> > +	enum intel_pch ret = PCH_NOP;
> > +
> > +	/*
> > +	 * In a virtualized passthrough environment we can be in a
> > +	 * setup where the ISA bridge is not able to be passed through.
> > +	 * In this case, a south bridge can be emulated and we have to
> > +	 * make an educated guess as to which PCH is really there.
> > +	 */
> > +
> > +	if (IS_GEN5(dev)) {
> > +		ret = PCH_IBX;
> > +		DRM_DEBUG_KMS("Assuming Ibex Peak PCH\n");
> > +	} else if (IS_GEN6(dev) || IS_IVYBRIDGE(dev)) {
> > +		ret = PCH_CPT;
> > +		DRM_DEBUG_KMS("Assuming CouarPoint PCH\n");
> > +	} else if (IS_HASWELL(dev) || IS_BROADWELL(dev)) {
> > +		ret = PCH_LPT;
> > +		DRM_DEBUG_KMS("Assuming LynxPoint PCH\n");
> > +	} else if (IS_SKYLAKE(dev)) {
> > +		ret = PCH_SPT;
> > +		DRM_DEBUG_KMS("Assuming SunrisePoint PCH\n");
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  void intel_detect_pch(struct drm_device *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > @@ -503,6 +531,8 @@ void intel_detect_pch(struct drm_device *dev)
> >  				dev_priv->pch_type = PCH_SPT;
> >  				DRM_DEBUG_KMS("Found SunrisePoint LP PCH\n");
> >  				WARN_ON(!IS_SKYLAKE(dev));
> > +			} else if (id == INTEL_PCH_P2X_DEVICE_ID_TYPE) {
> > +				dev_priv->pch_type = intel_virt_detect_pch(dev);
> >  			} else
> >  				continue;
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 8c93845..6eb0230 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2584,6 +2584,7 @@ struct drm_i915_cmd_table {
> >  #define INTEL_PCH_LPT_LP_DEVICE_ID_TYPE		0x9c00
> >  #define INTEL_PCH_SPT_DEVICE_ID_TYPE		0xA100
> >  #define INTEL_PCH_SPT_LP_DEVICE_ID_TYPE		0x9D00
> > +#define INTEL_PCH_P2X_DEVICE_ID_TYPE		0x7100
> >
> >  #define INTEL_PCH_TYPE(dev) (__I915__(dev)->pch_type)
> >  #define HAS_PCH_SPT(dev) (INTEL_PCH_TYPE(dev) == PCH_SPT)
> >
> 
> Assuming Kevin is ok with this:
> Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

Yes, I'm OK with this change. Just one comment. Does it make
sense to always have the guess as the fallback, instead of only
for P2X? If native side is OK with this, it will remove the need 
to add more IDs for different hypervisors in the future...

Thanks
Kevin