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

[Jesse Barnes]

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.

Jesse