Re: [PATCH v4 00/11] virtio-iommu: Add ACPI support

[Haiwei Li <lihaiwei.kernel@gmail.com>]

On Tue, Oct 12, 2021 at 1:34 AM Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:
>
> Hi Haiwei,
>
> On Mon, Oct 11, 2021 at 06:10:07PM +0800, Haiwei Li wrote:
> [...]
> > Gave up waiting for root file system device.  Common problems:
> >  - Boot args (cat /proc/cmdline)
> >    - Check rootdelay= (did the system wait long enough?)
> >  - Missing modules (cat /proc/modules; ls /dev)
> > ALERT!  UUID=3caf26b5-4d08-43e0-8634-7573269c4f70 does not exist.
> > Dropping to a shell!
> >
> > Any suggestions? Thanks.
>
> It's possible that the rootfs is on a disk behind the IOMMU, and the IOMMU
> driver doesn't get loaded. That could happen, for example, if the
> virtio-iommu module is not present in the initramfs. Since IOMMU drivers
> are typically built into the kernel rather than modules, distro tools that
> build the initramfs might not pick up IOMMU modules. I'm guessing this
> could be the issue here because of the hints and "Dropping to a shell"
> line.
>
> The clean solution will be to patch the initramfs tools to learn about
> IOMMU drivers (I'm somewhat working on that). In the meantime, if this is
> indeed the problem, you could try explicitly adding the virtio-iommu
> module to the initramfs, or building the kernel with CONFIG_VIRTIO_IOMMU=y
> rather than =m, though that requires VIRTIO and VIRTIO_PCI to be built-in
> as well.

Thanks, Jean. It works.

--
Haiwei