LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Stephane Eranian <eranian@hpl.hp.com>
To: linux-kernel@vger.kernel.org
Cc: ak@suse.de, akpm@linux-foundation.org
Subject: Re: [PATCH] i386 make NMI use PERFCTR1 for architectural perfmon (take 2)
Date: Mon, 19 Feb 2007 14:32:06 -0800	[thread overview]
Message-ID: <20070219223206.GA30469@frankl.hpl.hp.com> (raw)
In-Reply-To: <20070217160656.GA16715@frankl.hpl.hp.com>

Hello,

This patch against 2.6.20-git14 makes the NMI watchdog use PERFSEL1/PERFCTR1
instead of PERFSEL0/PERFCTR0 on processors supporting Intel architectural
perfmon, such as Intel Core 2. Although all PMU events can work on
both counters, the Precise Event-Based Sampling (PEBS) requires that the
event be in PERFCTR0 to work correctly (see section 18.14.4.1 in the
IA32 SDM Vol 3b).

A similar patch for x86-64 is to follow.

Changelog:
        - make the i386 NMI watchdog use PERFSEL1/PERFCTR1 instead of PERFSEL0/PERFCTR0
          on processors supporting the Intel architectural perfmon (e.g. Core 2 Duo).
          This allows PEBS to work when the NMI watchdog is active.

signed-off-by: stephane eranian <eranian@hpl.hp.com>


diff -urNp --exclude=.git linux-2.6.20.orig/arch/i386/kernel/nmi.c linux-2.6.20.base/arch/i386/kernel/nmi.c
--- linux-2.6.20.orig/arch/i386/kernel/nmi.c	2007-02-19 13:37:26.000000000 -0800
+++ linux-2.6.20.base/arch/i386/kernel/nmi.c	2007-02-19 13:54:42.000000000 -0800
@@ -307,7 +307,7 @@ static int __init check_nmi_watchdog(voi
 		nmi_hz = 1;
 
 		if (wd->perfctr_msr == MSR_P6_PERFCTR0 ||
-		    wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) {
+		    wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) {
 			nmi_hz = adjust_for_32bit_ctr(nmi_hz);
 		}
 	}
@@ -741,8 +741,8 @@ static int setup_intel_arch_watchdog(voi
 	    (ebx & ARCH_PERFMON_UNHALTED_CORE_CYCLES_PRESENT))
 		goto fail;
 
-	perfctr_msr = MSR_ARCH_PERFMON_PERFCTR0;
-	evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL0;
+	perfctr_msr = MSR_ARCH_PERFMON_PERFCTR1;
+	evntsel_msr = MSR_ARCH_PERFMON_EVENTSEL1;
 
 	if (!reserve_perfctr_nmi(perfctr_msr))
 		goto fail;
@@ -1022,7 +1022,7 @@ __kprobes int nmi_watchdog_tick(struct p
 				write_watchdog_counter(wd->perfctr_msr, NULL);
 	 		}
 			else if (wd->perfctr_msr == MSR_P6_PERFCTR0 ||
-				 wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR0) {
+				 wd->perfctr_msr == MSR_ARCH_PERFMON_PERFCTR1) {
 				/* P6 based Pentium M need to re-unmask
 				 * the apic vector but it doesn't hurt
 				 * other P6 variant.

      parent reply	other threads:[~2007-02-19 22:32 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-17 16:06 [PATCH] i386 make NMI use PERFCTR1 for architectural perfmon Stephane Eranian
2007-02-18 16:56 ` Andi Kleen
2007-02-19 16:36   ` Stephane Eranian
2007-02-19 16:38     ` Andi Kleen
2007-02-19 22:32 ` Stephane Eranian [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20070219223206.GA30469@frankl.hpl.hp.com \
    --to=eranian@hpl.hp.com \
    --cc=ak@suse.de \
    --cc=akpm@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [PATCH] i386 make NMI use PERFCTR1 for architectural perfmon (take 2)' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).