linux-kernel - Re: [PATCH v2] perf/x86: Fix HO/GO counting with SVM disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 29 Feb 2012 19:08:00 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, joro@...tes.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Stephane Eranian <eranian@...gle.com>,
	David Ahern <dsahern@...il.com>,
	Gleb Natapov <gleb@...hat.com>,
	Robert Richter <robert.richter@....com>
Subject: Re: [PATCH v2] perf/x86: Fix HO/GO counting with SVM disabled

On 02/29/2012 07:05 PM, Joerg Roedel wrote:
> On Wed, Feb 29, 2012 at 07:00:09PM +0200, Avi Kivity wrote:
> > On 02/29/2012 03:57 PM, Joerg Roedel wrote:
> > > It turned out that a performance counter on AMD does not
> > > count at all when the GO or HO bit is set in the control
> > > register and SVM is disabled in EFER.
> > >
> > > This patch works around this issue by masking out the HO bit
> > > in the performance counter control register when SVM is not
> > > enabled.
> > >
> > > The GO bit is not touched because it is only set when the
> > > user wants to count in guest-mode only. So when SVM is
> > > disabled the counter should not run at all and the
> > > not-counting is the intended behaviour.
> > >
> > > diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
> > > index 0397b23..67250a5 100644
> > > --- a/arch/x86/kernel/cpu/perf_event_amd.c
> > > +++ b/arch/x86/kernel/cpu/perf_event_amd.c
> > > @@ -1,4 +1,5 @@
> > >  #include <linux/perf_event.h>
> > > +#include <linux/export.h>
> > >  #include <linux/types.h>
> > >  #include <linux/init.h>
> > >  #include <linux/slab.h>
> > > @@ -357,7 +358,9 @@ static void amd_pmu_cpu_starting(int cpu)
> > >  	struct amd_nb *nb;
> > >  	int i, nb_id;
> > >  
> > > -	if (boot_cpu_data.x86_max_cores < 2)
> > > +	cpuc->perf_ctr_virt_mask = AMD_PERFMON_EVENTSEL_HOSTONLY;
> > > +
> > > +	if (boot_cpu_data.x86_max_cores < 2 || boot_cpu_data.x86 == 0x15)
> > >  		return;
> > 
> > Why this (boot_cpu_data.x86 == 0x15) change?
>
> This is because this function did not run on Fam15h before but now it
> has to so that cpuc->perf_ctr_virt_mask is initialized. The other stuff
> done in this function is setup for northbridge counter. These are not
> yet implemented for Fam15h CPUs so this setup must not run on those
> CPUs. Therefore the check was added.
> Once northbridge counters are implemented for Fam15h this check can go
> away again.
>

Thanks.  Ingo, this had better go through tip.git since most of the
changes are perf related.

-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/