Re: [regression, bisected, pci/iommu] Bug 216865 - Black screen when amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled

[Felix Kuehling]

[+Suravee]

Am 2023-02-16 um 00:37 schrieb Vasant Hegde:
> Hi Jason,
>
>
> On 2/16/2023 6:14 AM, Jason Gunthorpe wrote:
>> On Wed, Feb 15, 2023 at 07:35:45PM -0500, Felix Kuehling wrote:
>>> If I understand this correctly, the HW or the BIOS is doing something wrong
>>> about reporting ACS. I don't know what the GPU driver can do other than add
>>> some quirk to stop using AMD IOMMUv2 on this HW/BIOS.
>> How about this:
>>
>> diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
>> index 864e4ffb6aa94e..cc027ce9a6e86f 100644
>> --- a/drivers/iommu/amd/iommu_v2.c
>> +++ b/drivers/iommu/amd/iommu_v2.c
>> @@ -732,6 +732,7 @@ EXPORT_SYMBOL(amd_iommu_unbind_pasid);
>>   
>>   int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
>>   {
>> +	struct iommu_dev_data *dev_data = dev_iommu_priv_get(&pdev->dev);
>>   	struct device_state *dev_state;
>>   	struct iommu_group *group;
>>   	unsigned long flags;
>> @@ -740,6 +741,9 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
>>   
>>   	might_sleep();
>>   
>> +	if (!dev_data->ats.enabled)
>> +		return -EINVAL;
>> +
> Thanks for the proposed fix. But aactually this will not solve the issue because
> current flow is :
>    - in this function it tries to allocate new domain
>    - Calls iommu_attach_group() which will call attach_device. In that path
>      it will try to enable ATS/PASID and hitting error.
>
> As I mentioned in other reply I think even current code returns error from
> amd_iommu_init_device() to GPU. But the issue is, in __iommu_attach_group() path
> it detached device from current domain, failed to attach to new domain and
> returned error. We didn't put the device back to old domain thats causing the
> issue. Below series should fix this issue.
>
> https://lore.kernel.org/linux-iommu/20230215052642.6016-1-vasant.hegde@amd.com/
>
> -Vasant
>