Re: "dma-mapping: remove CONFIG_DMA_REMAP" causes AMD SME boot fail

Christoph Hellwig
2022-03-30T17:55:34Z

On Wed, Mar 30, 2022 at 01:51:07PM -0400, Alex Xu (Hello71) wrote:
> Hi,
>
> After a recent kernel update, booting one of my machines causes it to
> hang on a black screen. Pressing Lock keys on the USB keyboard does not
> turn on the indicators, and the machine does not appear on the Ethernet
> network. I don't have a serial port on this machine. I didn't try
> netconsole, but I suspect it won't work.
>
> Setting mem_encrypt=0 seems to resolve the issue. Reverting f5ff79fddf0e
> ("dma-mapping: remove CONFIG_DMA_REMAP") also appears to resolve the
> issue.
>
> The machine in question has an AMD Ryzen 5 1600 and ASRock B450 Pro4.

This looks like something in the AMD IOMMU code or it's users can't
deal with vmalloc addresses. I'll start looking for a culprit ASAP.