[Xen-changelog] [xen-4.2-testing] x86/amd: Fix xen_apic_write warnings in Dom0

[Xen patchbot-4.2-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Wei Wang <wei.wang2@xxxxxxx>
# Date 1351171261 -7200
# Node ID 36fce7db3b3120b42ec60efad348c89dce4c4dcd
# Parent  27db446078b50d576d8425d36daf52f886b710e6
x86/amd: Fix xen_apic_write warnings in Dom0

[    0.020294] ------------[ cut here ]------------
[    0.020311] WARNING: at arch/x86/xen/enlighten.c:730
xen_apic_write+0x15/0x17()
[    0.020318] Hardware name: empty
[    0.020323] Modules linked in:
[    0.020334] Pid: 1, comm: swapper/0 Not tainted 3.3.8 #7
[    0.020340] Call Trace:
[    0.020354]  [<ffffffff81050379>] warn_slowpath_common+0x80/0x98
[    0.020369]  [<ffffffff810503a6>] warn_slowpath_null+0x15/0x17
[    0.020378]  [<ffffffff810034df>] xen_apic_write+0x15/0x17
[    0.020392]  [<ffffffff8101cb2b>] perf_events_lapic_init+0x2e/0x30
[    0.020410]  [<ffffffff81ee4dd0>] init_hw_perf_events+0x250/0x407
[    0.020419]  [<ffffffff81ee4b80>] ? check_bugs+0x2d/0x2d
[    0.020430]  [<ffffffff81002181>] do_one_initcall+0x7a/0x131
[    0.020444]  [<ffffffff81edbbf9>] kernel_init+0x91/0x15d
[    0.020456]  [<ffffffff817caaa4>] kernel_thread_helper+0x4/0x10
[    0.020471]  [<ffffffff817c347c>] ? retint_restore_args+0x5/0x6
[    0.020481]  [<ffffffff817caaa0>] ? gs_change+0x13/0x13
[    0.020500] ---[ end trace a7919e7f17c0a725 ]---

Kernel function check_hw_exists() writes 0xabcd to msr 0xc0010201 (Performance 
Event
Counter 0) and read it again to check if it is running as dom0. Early amd cpus 
does
not reset perf counters during warm reboot. If the kernel is booted with bare 
metal
and then as a dom0, the content of msr 0xc0010201 will stay and the checking 
will
pass and PMU will be enabled unexpectedly.

Signed-off-by: Wei Wang <wei.wang2@xxxxxxx>

Don't reset the counters when used for the NMI watchdog.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
xen-unstable changeset: 26054:983108e1b56b
xen-unstable date: Mon Oct 15 13:03:36 UTC 2012
---


diff -r 27db446078b5 -r 36fce7db3b31 xen/arch/x86/cpu/amd.c
--- a/xen/arch/x86/cpu/amd.c    Fri Oct 05 12:55:27 2012 +0200
+++ b/xen/arch/x86/cpu/amd.c    Thu Oct 25 15:21:01 2012 +0200
@@ -11,6 +11,7 @@
 #include <asm/hvm/support.h>
 #include <asm/setup.h> /* amd_init_cpu */
 #include <asm/acpi.h>
+#include <asm/apic.h>
 
 #include "cpu.h"
 
@@ -532,6 +533,17 @@ static void __devinit init_amd(struct cp
        if (c->x86 > 0x11)
                set_bit(X86_FEATURE_ARAT, c->x86_capability);
 
+       /*
+        * Prior to Family 0x14, perf counters are not reset during warm reboot.
+        * We have to reset them manually.
+        */
+       if (nmi_watchdog != NMI_LOCAL_APIC && c->x86 < 0x14) {
+               wrmsrl(MSR_K7_PERFCTR0, 0);
+               wrmsrl(MSR_K7_PERFCTR1, 0);
+               wrmsrl(MSR_K7_PERFCTR2, 0);
+               wrmsrl(MSR_K7_PERFCTR3, 0);
+       }
+
        if (cpuid_edx(0x80000007) & (1 << 10)) {
                rdmsr(MSR_K7_HWCR, l, h);
                l |= (1 << 27); /* Enable read-only APERF/MPERF bit */

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