Re: port-xen/58561 (panic: kernel diagnostic assertion, "x86_read_psl() == 0" failed: file, "/home/netbsd/10/src/sys/arch/x86/x86/pmap.c", line 3581)

["Konrad Schroder via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR port-xen/58561; it has been noted by GNATS.

From: Konrad Schroder <perseant%hhhh.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: port-xen-maintainer%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
 gnats-admin%netbsd.org@localhost, riastradh%NetBSD.org@localhost, campbell+netbsd%mumble.net@localhost,
 cherry%NetBSD.org@localhost
Subject: Re: port-xen/58561 (panic: kernel diagnostic assertion,
 "x86_read_psl() == 0" failed: file,
 "/home/netbsd/10/src/sys/arch/x86/x86/pmap.c", line 3581)
Date: Fri, 9 Jan 2026 07:24:17 -0800

 I can reliably reproduce this issue, quickly enough that a NetBSD 
 tools+release build usually will not complete before the system panics.  
 I am using yesterday's -current, with a kernel config as follows:
 
  Â  Â  netbsd# cat sys/arch/amd64/conf/LFS
  Â  Â  include "arch/amd64/conf/XEN3_DOMU"
 
      options         LOCKDEBUG
 
 The host system is Ubuntu 22.04.5 running xen-hypervisor-4.16-amd64, and 
 the guest config is:
 
  Â  Â  linux# cat lfs
  Â  Â  name = "lfs"
  Â  Â  kernel = "/etc/xen/netbsd-lfs.gz"
  Â  Â  memory = 16384
  Â  Â  vcpus = 2
  Â  Â  vif = [ 'bridge=br0' ]
  Â  Â  disk = [ '/dev/md3p6,raw,hda,rw' ]
 
  Â  Â  on_poweroff = 'destroy'
      on_reboot   = 'destroy'
      on_crash    = 'destroy'
 
 The load running on the system is from
 
  Â  Â  ./build.sh -j4 -U -u -O obj.amd64 tools release
 
 in a freshly unpacked src.
 
 If I configure the VM with "vcpus = 1", or turn off LOCKDEBUG, it 
 doesn't panic.
 
 (As the names imply, I'm hoping to use this configuration to test LFS, 
 but the problem is unrelated: the system panics without any LFS file 
 system ever having been active since boot.)
 
 The panic traces vary, but are consistent after the call to copyout():
 
  Â  Â  [ 842.2695658] panic: kernel diagnostic assertion "(psl = 
 x86_read_psl()) == 0" failed: file 
 "/home/src-current/sys/arch/x86/x86/pmap.c", line 3596 psl=0x1
  Â  Â  [ 842.2695658] cpu1: Begin traceback...
  Â  Â  [ 842.2695658] vpanic() at netbsd:vpanic+0x164
  Â  Â  [ 842.2695658] kern_assert() at netbsd:kern_assert+0x4b
  Â  Â  [ 842.2695658] pmap_load() at netbsd:pmap_load+0x13d
  Â  Â  [ 842.2695658] do_pmap_load() at netbsd:do_pmap_load+0x1d
  Â  Â  [ 842.2695658] copyout() at netbsd:copyout+0x48
  Â  Â  [ 842.2695658] ubc_uiomove() at netbsd:ubc_uiomove+0x12e
  Â  Â  [ 842.2695658] ffs_read() at netbsd:ffs_read+0xf0
  Â  Â  [ 842.2695658] VOP_READ() at netbsd:VOP_READ+0x3c
  Â  Â  [ 842.2695658] vn_rdwr() at netbsd:vn_rdwr+0x100
  Â  Â  [ 842.2695658] vmcmd_readvn() at netbsd:vmcmd_readvn+0x56
  Â  Â  [ 842.2695658] execve_runproc() at netbsd:execve_runproc+0x34e
  Â  Â  [ 842.2695658] execve1() at netbsd:execve1+0x4c
  Â  Â  [ 842.2695658] sys_execve() at netbsd:sys_execve+0x2a
  Â  Â  [ 842.2695658] syscall() at netbsd:syscall+0x98
  Â  Â  [ 842.2695658] --- syscall (number 59) ---
  Â  Â  [ 842.2695658] netbsd:syscall+0x98:
  Â  Â  [ 842.2695658] cpu1: End traceback...
 
 Let me know if there is anything you'd like me to do to help test or 
 further diagnose the issue.
 
 Thanks,
 
 Konrad Schroder
 perseant%hhhh.org@localhost