Pkg xen devel - Jan 2013 - Bug#698651: xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be unexpectedly enabled on Dom0

Package: xen-hypervisor-4.1-amd64
Version: 4.1.3-7
Severity: important
Tags: patch

Dear Maintainer,

The PMU may be enabled on the Dom0 although the needed MSRs are not
accessible, causing at least major noise on the xen messages ring
buffer. I suspect there might also be a performance decrease, because
the MSR write is trapped by Xen.

Once the PC is in that state, a reboot won't help.

This bug is fixed in Xen upstream:
 
http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=cabea9d59f1783167a79fa7a550ced04b3506f3c

I've successfully tested this patch on the debian kernel from wheezy.

How to reproduce:
  - boot bare metal kernel (that is, no xen hypervisor)
  - (re)boot dom0 with xen

This results in the following kernel warning:
  [    0.016036] ------------[ cut here ]------------
  [    0.016070] WARNING: at
/build/buildd-linux_3.2.35-2-amd64-v9djlH/linux-3.2.35/arch/x86/xen/enlighten.c:738
init_hw_perf_events+0x246/0x3e1()
  [    0.016107] Hardware name: MS-7368
  [    0.016135] Modules linked in:
  [    0.016189] Pid: 1, comm: swapper/0 Not tainted 3.2.0-4-amd64 #1 Debian
3.2.35-2
  [    0.016224] Call Trace:
  [    0.016257]  [<ffffffff81046a75>] ? warn_slowpath_common+0x78/0x8c
  [    0.016289]  [<ffffffff816b2f72>] ? init_hw_perf_events+0x246/0x3e1
  [    0.016319]  [<ffffffff816b2d2c>] ? check_bugs+0x2b/0x2b
  [    0.016351]  [<ffffffff81002085>] ? do_one_initcall+0x75/0x12c
  [    0.016383]  [<ffffffff816abbcb>] ? kernel_init+0x8d/0x152
  [    0.016414]  [<ffffffff81354174>] ? kernel_thread_helper+0x4/0x10
  [    0.016447]  [<ffffffff81352233>] ? int_ret_from_sys_call+0x7/0x1b
  [    0.016479]  [<ffffffff8134d37c>] ? retint_restore_args+0x5/0x6
  [    0.016509]  [<ffffffff81354170>] ? gs_change+0x13/0x13
  [    0.016545] ---[ end trace 4fbe30a09b2591f0 ]---
  [    0.016576] ... version:                0
  [    0.016605] ... bit width:              48
  [    0.016633] ... generic registers:      4
  [    0.016662] ... value mask:             0000ffffffffffff
  [    0.016691] ... max period:             00007fffffffffff
  [    0.016721] ... fixed-purpose events:   0
  [    0.016749] ... event mask:             000000000000000f
  [    0.016971] NMI watchdog enabled, takes one hw-pmu counter.
  [    0.017012] ------------[ cut here ]------------

and the following (repeating) output on the xen messages ring buffer:
  (XEN) printk: 28 messages suppressed.
  (XEN) traps.c:2488:d0 Domain attempted WRMSR 00000000c0010000 from
0x0000000000130076 to 0x0000000000530076.
  (XEN) printk: 52 messages suppressed.
  (XEN) traps.c:2488:d0 Domain attempted WRMSR 00000000c0010000 from
0x0000000000130076 to 0x0000000000530076.
  (XEN) printk: 27 messages suppressed.
[..]


-- System Information:
Debian Release: 7.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

xen-hypervisor-4.1-amd64 depends on no packages.

Versions of packages xen-hypervisor-4.1-amd64 recommends:
ii  xen-utils-4.1  4.1.3-7

Versions of packages xen-hypervisor-4.1-amd64 suggests:
ii  xen-docs-4.1  4.1.3-7

-- no debconf information

Your message dated Thu, 31 Jan 2013 15:03:48 +0000
with message-id <E1U0vg4-0004AW-B8 at franck.debian.org>
and subject line Bug#698651: fixed in xen 4.1.4-1
has caused the Debian Bug report #698651,
regarding xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be
unexpectedly enabled on Dom0
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
message is talking about, this may indicate a serious mail system
misconfiguration somewhere. Please contact owner at bugs.debian.org
immediately.)


-- 
698651: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=698651
Debian Bug Tracking System
Contact owner at bugs.debian.org with problems
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Subject: xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be
unexpectedly enabled on Dom0
Date: Mon, 21 Jan 2013 19:36:52 +0100
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Subject: Bug#698651: fixed in xen 4.1.4-1
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