[Bug 262573] PKU CPU instruction causing kernel panics when FreeBSD Guest OS, using Zen 3 host processor and QEMU hypervisor.

From: <bugzilla-noreply_at_freebsd.org>
Date: Tue, 15 Mar 2022 16:34:12 UTC 
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=262573

            Bug ID: 262573
           Summary: PKU CPU instruction causing kernel panics when FreeBSD
                    Guest OS, using Zen 3 host processor and QEMU
                    hypervisor.
           Product: Base System
           Version: 12.2-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: chrysalis@chrysalisnet.org

PKU is new in Zen3, I recently migrated a system from a 2600X CPU to a 5600G
CPU.

I then discovered in any guest machine running a variant of FreeBSD, it was
very easy and repeatedly with certain binaries, and services to cause a kernel
panic.

I was able to nail it down to PKU by changing the cpu type to EPYC (which is
close to Zen 1), and then manually adding Zen 3 instructions one at a time,
this process eventually confirmed it was PKU.

I have not yet tested FreeBSD 13 but plan to.  When I test it, if it has the
same problem I will post details of the actual panic and how to repeat.

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