Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1216622

Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is patching the handler

Show all headers | View raw

On Sun, Aug 30, 2015 at 10:37:57PM -0400, Chuck Ebbert wrote:
> This is from https://bugzilla.redhat.com/show_bug.cgi?id=1258223
> 
> [    0.036000] BUG: unable to handle kernel paging request at 55501e06
[...]
> [    0.036000]  [<c0409c80>] ? add_nops+0x90/0xa0
> [    0.036000]  [<c040a054>] apply_alternatives+0x274/0x630
> [    0.036000]  [<c07f1cf0>] ? wait_for_xmitr+0xa0/0xa0
> [    0.036000]  [<c071a6fc>] ? sprintf+0x1c/0x20
> [    0.036000]  [<c0aae480>] ? irq_entries_start+0x698/0x698
> [    0.036000]  [<c071be4b>] ? memcpy+0xb/0x30
> [    0.036000]  [<c07f3950>] ? serial8250_set_termios+0x20/0x20
[...]
> Interrupt 0x30 occurred while the alternatives code was replacing the
> initial 0x90,0x90,0x90 NOPs (from the ASM_CLAC macro) with the optimized
> version, 0x8d,0x76,0x00. Only the first byte has been replaced so far,
> and it makes a mess out of the insn decoding.

Chuck, thanks for reporting this.

I have only been able to reproduce this so far using qemu and TCG (not
KVM) which of course raises a range of questions: could it be a qemu
bug or a TCG bug?  Could it be that an atomic op is not correctly
implemented by qemu?  I will keep trying on KVM.  Because I don't have
a convenient server with 32 bit kernel and a serial port that I can
reboot thousands of times, I have not tried to reproduce on baremetal yet.

Here's how to reproduce it.  (The host can be x86-64)

(1) Grab the 32 bit Fedora kernel we are using from
https://kojipkgs.fedoraproject.org//packages/kernel/4.2.0/1.fc24/i686/kernel-core-4.2.0-1.fc24.i686.rpm
(from http://koji.fedoraproject.org/koji/buildinfo?buildID=681723)

(2) Unpack it to extract vmlinuz:

cd /tmp
rpm2cpio /mnt/scratch/kernel-core-4.2.0-1.fc24.i686.rpm | cpio -id
cp ./lib/modules/4.2.0-1.fc24.i686/vmlinuz .

(3) Boot the kernel under qemu/KVM.  The following single line command
repeatedly boots the kernel until the bug is hit:

while qemu-system-x86_64 -nographic -no-reboot -M accel=kvm:tcg -kernel vmlinuz -append 'console=ttyS0 panic=1' -serial stdio -monitor none >& log; ! grep add_nops log; do echo -n .; done

It takes many iterations (100s with TCG) to hit the bug.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Chuck Ebbert <cebbert.lkml@gmail.com> - 2015-08-31 04:40 +0200
  Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler "Richard W.M. Jones" <rjones@redhat.com> - 2015-09-01 08:30 +0200
    Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Thomas Gleixner <tglx@linutronix.de> - 2015-09-02 11:20 +0200
      Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler "Richard W.M. Jones" <rjones@redhat.com> - 2015-09-02 21:10 +0200
        Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler "Richard W.M. Jones" <rjones@redhat.com> - 2015-09-03 10:00 +0200
      Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Borislav Petkov <bp@alien8.de> - 2015-09-03 11:00 +0200
        Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Thomas Gleixner <tglx@linutronix.de> - 2015-09-03 12:50 +0200
          Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-03 14:50 +0200
            Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Thomas Gleixner <tglx@linutronix.de> - 2015-09-03 15:10 +0200
          Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler "Richard W.M. Jones" <rjones@redhat.com> - 2015-09-03 18:00 +0200
          [tip:x86/urgent] x86/alternatives: Make optimize_nops()   interrupt safe and synced tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2015-09-03 21:40 +0200
          Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler "Richard W.M. Jones" <rjones@redhat.com> - 2015-09-04 09:50 +0200
          Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Borislav Petkov <bp@alien8.de> - 2015-09-04 14:10 +0200
            Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Thomas Gleixner <tglx@linutronix.de> - 2015-09-04 15:40 +0200
              Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is  patching the handler Borislav Petkov <bp@alien8.de> - 2015-09-05 17:30 +0200

csiph-web