Re: [[RESEND] iommufd PATCH v2 1/2] i915/gvt: Move gvt mapping cache initialization to intel_vgpu_init_dev()

[Yi Liu <yi.l.liu@intel.com>]

On 2022/12/1 11:25, Zhenyu Wang wrote:
> On 2022.11.29 02:58:30 -0800, Yi Liu wrote:
>> vfio container registers .dma_unmap() callback after the device is opened.
>> So it's fine for mdev drivers to initialize internal mapping cache in
>> .open_device(). See vfio_device_container_register().
>>
>> Now with iommufd an access ops with an unmap callback is registered
>> when the device is bound to iommufd which is before .open_device()
>> is called. This implies gvt's .dma_unmap() could be called before its
>> internal mapping cache is initialized.
>>
>> The fix is moving gvt mapping cache initialization to vGPU init. While
>> at it also move ptable initialization together.
>>
>> Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
>> Cc: Zhi Wang <zhi.a.wang@intel.com>
>> Cc: Kevin Tian <kevin.tian@intel.com>
>> Cc: intel-gvt-dev@lists.freedesktop.org
>> Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> ---
>>   drivers/gpu/drm/i915/gvt/kvmgt.c | 13 +++++++++----
>>   1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> index 7a45e5360caf..f563e5dbe66f 100644
>> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
>> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> @@ -671,9 +671,6 @@ static int intel_vgpu_open_device(struct vfio_device *vfio_dev)
>>   
>>   	vgpu->attached = true;
>>   
>> -	kvmgt_protect_table_init(vgpu);
>> -	gvt_cache_init(vgpu);
>> -
>>   	vgpu->track_node.track_write = kvmgt_page_track_write;
>>   	vgpu->track_node.track_flush_slot = kvmgt_page_track_flush_slot;
>>   	kvm_page_track_register_notifier(vgpu->vfio_device.kvm,
>> @@ -1451,9 +1448,17 @@ static int intel_vgpu_init_dev(struct vfio_device *vfio_dev)
>>   	struct intel_vgpu *vgpu = vfio_dev_to_vgpu(vfio_dev);
>>   	struct intel_vgpu_type *type =
>>   		container_of(mdev->type, struct intel_vgpu_type, type);
>> +	int ret;
>>   
>>   	vgpu->gvt = kdev_to_i915(mdev->type->parent->dev)->gvt;
>> -	return intel_gvt_create_vgpu(vgpu, type->conf);
>> +	ret = intel_gvt_create_vgpu(vgpu, type->conf);
>> +	if (ret)
>> +		return ret;
>> +
>> +	kvmgt_protect_table_init(vgpu);
>> +	gvt_cache_init(vgpu);
>> +
>> +	return 0;
> 
> I'm fine with this change, but could we add some sanity check at close
> time to ensure we clean up any internal cache? Btw, do we need to reset
> rbtree root pointer?

I noticed there is gvt_cache_destroy() in intel_vgpu_close_device(). This
cleans up the internal cache. So even the rbtree root is valid, it is an
empty per close_device(). isn't it?

>>   }
>>   
>>   static void intel_vgpu_release_dev(struct vfio_device *vfio_dev)
>> -- 
>> 2.34.1
>>

-- 
Regards,
Yi Liu