Re: Linux 5.13+ as Xen dom0 crashes on Ryzen CPU (ucode loading related?)

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Tue, Sep 14, 2021 at 10:39:10AM +0200, Jan Beulich wrote:
> On 14.09.2021 09:14, Juergen Gross wrote:
> > On 13.09.21 14:50, Marek Marczykowski-Górecki wrote:
> >> Hi,
> >>
> >> Since 5.13, the Xen (PV) dom0 crashes on boot, before even printing the
> >> kernel version.
> >> Test environment:
> >>   - Xen 4.14.2
> >>   - AMD Ryzen 5 4500U (reported also on AMD Ryzen 7 4750U)
> >>   - Linux 5.13.13, confirmed also on 5.14
> >>
> >> The crash happens only if the initramfs has earlycpio with microcode.
> >> I don't have a serial console, but I've got a photo with crash message
> >> (from Xen, Linux doesn't managed to print anything):
> >> https://user-images.githubusercontent.com/726704/133084966-5038f37e-001b-4688-9f90-83d09be3dc2d.jpg
> >>
> >> Transcription of some of it:
> >>
> >>      mapping kernel into physical memory
> >>      about to get started
> >>      (XEN) Pagetable walk from ffffffff82810888:
> >>      (XEN)  L4[0x1ff] = 0000000332815067 0000000000002815
> >>      (XEN)  L3[0x1fe] = 0000000332816067 0000000000002816
> >>      (XEN)  L2[0x014] = 0000000334018067 0000000000004018
> >>      (XEN)  L1[0x010] = 0000000332810067 0000000000002810
> >>      (XEN) domain_crash_sync called from entry.S: fault at ffff82d04033e790 x86_64/entry.S#domain_crash_page_fault
> >>      (XEN) Domain 0 (vcpu#0) crashed on cpu#0:
> >>      (XEN) ----[ Xen-4.14.2  x86_64  debug=n  Not tainted ]----
> >>      (XEN) CPU:    0
> >>      (XEN) RIP:    e033:[<0000000000000000>]
> > 
> > The domain's run state seems to be completely clobbered.
> > 
> > Did you try to boot the kernel with "earlyprintk=xen" to get some idea
> > how far it progressed?
> 
> I guess without my "xen/x86: allow "earlyprintk=xen" to work for PV Dom0"
> "earlyprintk=xen" would need to be accompanied by "console=xenboot". I
> have not tried whether this helps, this is merely a guess from having
> looked at the code relatively recently.

This boot was with "earlyprintk=xen" already, but I didn't know
about "console=xenboot".
Anyway, it seems it isn't relevant anymore.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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