Re: [Xen-devel] [BUG] panic: "IO-APIC + timer doesn't work" - several people have reproduced

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.01.2020 01:35,  Aaron Janse  wrote:
> On Fri, Jan 3, 2020, at 4:51 AM, Jan Beulich wrote:
>> Did you try disabling use of the IOMMU ("iommu=0" on the Xen
>> command line)?
> 
> Unfortunately, Qubes requires iommu. Setting "iommu=0" results in a panic:
> 
> ```
> Couldn't enable IOMMU and iommu=required/force
> ```

Since this isn't the upstream default, there are two options: Either
you simply have e.g. "iommu=force" elsewhere on the command line - in
this case simply delete the option for this experimenting. Or they've
patched their sources to this effect, in which case you'll want to
undo that source change.

> I couldn't find anywhere to disable the flag (even though it would break
> Qubes, at least the flag could help minimize the scope of the cause of the
> timer crash).
> 
> I installed Xen on Arch Linux in order to test this flag, but I'm having
> the same problem I had on Ubuntu: booting to Xen hangs on loading
> initramfs. [1]

Booting which exact version of Xen? Iirc these initramfs issues
(with LZ4 compression) have been fixed on 4.13.0 as well as
4.12.2. Also you may not have realized that _any_ initramfs (or
Dom0 kernel image) issue could be avoided for the purposes here
by simply omitting them from the directives issued to grub -
after all you don't get as far as booting Dom0.

Jan

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