Linux kernel: powerpc: KVM guest can trigger host crash on Power8

[John Paul Adrian Glaubitz]

Hi Michael!

On 10/27/21 07:30, Michael Ellerman wrote:
> I did test the repro case you gave me before (in the bugzilla), which
> was building glibc, that passes for me with a patched host.

Did you manage to crash the unpatched host? If the unpatched host crashes
for you but the patched doesn't, I will make sure I didn't accidentally
miss anything.

Also, I'll try a kernel from git with Debian's config.

> I guess we have yet another bug.
> 
> I tried the following in a debian BE VM and it completed fine:
> 
>  $ dget -u http://ftp.debian.org/debian/pool/main/g/git/git_2.33.1-1.dsc
>  $ sbuild -d sid --arch=powerpc --no-arch-all git_2.33.1-1.dsc
> 
> Same for ppc64.
> 
> And I also tried both at once, repeatedly in a loop.

Did you try building gcc-11 for powerpc and ppc64 both at once?

> I guess it's something more complicated.
> 
> What exact host/guest kernel versions and configs are you running?

Both the host and guest are running Debian's stock 5.14.12 kernel. The host has
a kernel with your patches applied, the guest doesn't.

Let me do some more testing.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
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