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

From: Baolu Lu
Date: Thu Jan 05 2023 - 05:38:31 EST


On 2023/1/5 18:27, Vasant Hegde wrote:
On 1/5/2023 6:39 AM, Matt Fagnani wrote:
I built 6.2-rc2 with the patch applied. The same black screen problem happened
with 6.2-rc2 with the patch. I tried to use early kdump with 6.2-rc2 with the
patch twice by panicking the kernel with sysrq+alt+c after the black screen
happened. The system rebooted after about 10-20 seconds both times, but no kdump
and dmesg files were saved in /var/crash. I'm attaching the lspci -vvv output as
requested.

Thanks for testing. As mentioned earlier I was not expecting this patch to fix
the black screen issue. It should fix kernel warnings and IOMMU page fault
related call traces. By any chance do you have the kernel boot logs?


@Baolu,
Looking into lspci output, it doesn't list ACS feature for Graphics card. So
with your fix it didn't enable PASID and hence it failed to boot.

So do you mind telling why does the PASID need to be enabled for the
graphic device? Or in another word, what does the graphic driver use the
PASID for?

--
Best regards,
baolu