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

[Jesse Barnes]

On 09/25/2015 08:31 AM, Jesse Barnes wrote:
> On 09/24/2015 08:41 PM, Tian, Kevin wrote:
>>> 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...
> 
> Yeah, at this point I don't think we have mix & match cases to worry
> about, so we could guess based on the GPU type across the board.

On second thought, let's get this version merged first, then play with
assuming a bridge type in a later patch, in case that breaks something.

Jesse