Re: [PATCH 2/5] drm/i915/gvt: move intel iommu detection to intel_gvt_init()

[Jike Song <jike.song@intel.com>]

On 01/11/2017 10:40 AM, Zhenyu Wang wrote:
> On 2017.01.11 10:18:30 +0800, Jike Song wrote:
>> On 01/10/2017 02:52 PM, Zhenyu Wang wrote:
>>> Prepare to remove detect_host() hook. Move intel iommu detection early
>>> in intel_gvt_init().
>>>
>>> Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/gvt/gvt.c   | 7 +++++++
>>>  drivers/gpu/drm/i915/gvt/kvmgt.c | 6 ------
>>>  2 files changed, 7 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c
>>> index 35264a991776..7a7886644acf 100644
>>> --- a/drivers/gpu/drm/i915/gvt/gvt.c
>>> +++ b/drivers/gpu/drm/i915/gvt/gvt.c
>>> @@ -73,6 +73,13 @@ int intel_gvt_init_host(void)
>>>  	if (intel_gvt_host.initialized)
>>>  		return 0;
>>>  
>>> +#ifdef CONFIG_INTEL_IOMMU
>>> +	if (intel_iommu_gfx_mapped) {
>>> +		gvt_err("Hardware IOMMU compatibility not yet supported, try to boot with intel_iommu=igfx_off\n");
>>> +		return -ENODEV;
>>> +	}
>>> +#endif
>>> +
>>
>> Hi Zhenyu,
>>
>> Per my understanding, the "intel_iommu=" parameter acts only on native (think about XenGT),
>> so it's better to keep it somewhere in kvmgt.c, maybe kvmgt_init()?
>>
> 
> hmm, I think it's just a limit for current gvt device model but not related to hypervisor,
> and it would bail out to disable gvt only. Anyway we'll fix it soon so not worry much for that.
> 

I agree that it's only a temporary workaround, only want to point out that hypervisor does
matter: if we take XenGT considered, it has IOMMU hardware managed by Hypervisor, so its the
host (dom0) kernel doesn't need any special configuration for iommu :)

--
Thanks,
Jike
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