Re: [REGRESSION] Unable to pass AMD RX 6400 GPU via VFIO

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 20, 2026 at 12:42:04PM +0100, Thorsten Leemhuis wrote:
> @greg/@sasha: I might be missing something, but looks like one patch
> that was backported missed two series where it's needed (see below for
> details):
> 
> On 3/20/26 10:28, Mark Somerville wrote:
> > 
> > I run Debian 13 stable (6.12 kernel) and have encountered a regression.
> > 
> > My machine has three GPUs, the iGPU that is part of my 7950X and two dGPUs - one NVIDIA 3090 and one AMD RX 6400. I use the iGPU for the host and only use the two dGPUs with virtual machines via VFIO with libvirt.
> > 
> > Although I have specified kernel parameters vfio_pci.ids for the GPUs, I have not blacklisted the amdgpu driver so that the host iGPU can operate.  Previously, starting a VM with the RX 6400 dGPU assigned to it (via VFIO) would work fine. However, doing this with more recent stable kernels causes the machine to hang immediately (and then, ultimately, reset after a while - ~30s). No errors are logged, at least as things are configured just now.
> > 
> > I can reliably reproduce this crash and a bisection revealed the commit that introducted the problem: 8140ac7c55e75093a01c6110a2c4025fe7177c57.
> 
> That is 28695ca09d3264 ("drm/amd: Clean up kfd node on surprise
> disconnect") [v6.19-rc6, v6.18.7, v6.12.67 (as 8140ac7c55e750), v6.6.122].
> 
> A fix for that f7afda7fcd169a ("drm/amd: Fix hang on amdgpu unload by
> using pci_dev_is_disconnected()") [v7.0-rc1, v6.18.17, v6.12.77].
> 
> @greg/@sasha: Wondering why it's not in 6.19.y and 6.6.y. It failed
> there first, but later was applied to 6.18.y and 6.12.y:
> 
> https://lore.kernel.org/all/?q=%22Fix+hang+on+amdgpu+unload+by+using+pci_dev_is_disconnected%22+%28f%3Agreg+OR+f%3Asasha%29

It's in the queue for 6.6.y, I've queued it up for 6.19.y now too.

thanks,

greg k-h