[PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

[PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

[Stephane Eranian]

This patch fixes a bug introduced by commit 24223657.

The rdmsrl_safe() function returns 0 on success.
The current code was failing to detect the RAPL PMU
on real hardware  (missing /sys/devices/power) because
the return value of rdmsrl_safe() was misinterpreted.

Signed-off-by: Stephane Eranian <eranian@google.com>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 7c87424..619f769 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -543,7 +543,8 @@ static int rapl_cpu_prepare(int cpu)
 	if (phys_id < 0)
 		return -1;
 
-	if (!rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))
+	/* protect rdmsrl() to handle virtualization */
+	if (rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))
 		return -1;
 
 	pmu = kzalloc_node(sizeof(*pmu), GFP_KERNEL, cpu_to_node(cpu));

Re: [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

[Borislav Petkov]

On Wed, Apr 23, 2014 at 07:04:19PM +0200, Stephane Eranian wrote:
> 
> This patch fixes a bug introduced by commit 24223657.

Maybe add

Fixes: <commit-id>

tag?

> The rdmsrl_safe() function returns 0 on success.
> The current code was failing to detect the RAPL PMU
> on real hardware  (missing /sys/devices/power) because
> the return value of rdmsrl_safe() was misinterpreted.
> 
> Signed-off-by: Stephane Eranian <eranian@google.com>

Acked-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--

Re: [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

[Venkatesh Srinivas]

On Wed, Apr 23, 2014 at 12:00 PM, Borislav Petkov <bp@alien8.de> wrote:
> On Wed, Apr 23, 2014 at 07:04:19PM +0200, Stephane Eranian wrote:
>>
>> This patch fixes a bug introduced by commit 24223657.
>
> Maybe add
>
> Fixes: <commit-id>
>
> tag?
>
>> The rdmsrl_safe() function returns 0 on success.
>> The current code was failing to detect the RAPL PMU
>> on real hardware  (missing /sys/devices/power) because
>> the return value of rdmsrl_safe() was misinterpreted.
>>
>> Signed-off-by: Stephane Eranian <eranian@google.com>
>
> Acked-by: Borislav Petkov <bp@suse.de>

Brown-Paper-Bag-Worn-By: Venkatesh Srinivas <venkateshs@google.com>

-- vs;

Re: [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

[Andi Kleen]

> > Acked-by: Borislav Petkov <bp@suse.de>
> 
> Brown-Paper-Bag-Worn-By: Venkatesh Srinivas <venkateshs@google.com>

Again the bug is really in KVM. We wouldn't need all this crap
if KVM didn't throw the bogus #GPs. I'm sure you missed plenty
of MSR accesses elsewhere, and it's a ticking time bomb.

If the VM lies to the kernel with the family-model you need to at 
least limit the consequences. KVM is spectacularly failing
to do that by throwing bogus #GPs.

The brown paper bad needs to be employed on the KVM code
(or better the bug be fixed there, by defaulting to not #GP
on unknown MSRs)

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only

[tip:perf/urgent] perf/x86: Fix RAPL rdmsrl_safe() usage

[tip-bot for Stephane Eranian]

Commit-ID:  9f7ff8931e3c5ddc8535476971ec9501e9555c05
Gitweb:     http://git.kernel.org/tip/9f7ff8931e3c5ddc8535476971ec9501e9555c05
Author:     Stephane Eranian <eranian@google.com>
AuthorDate: Wed, 23 Apr 2014 19:04:19 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 24 Apr 2014 08:12:41 +0200

perf/x86: Fix RAPL rdmsrl_safe() usage

This patch fixes a bug introduced by:

  24223657806a ("perf/x86/intel: Use rdmsrl_safe() when initializing RAPL PMU")

The rdmsrl_safe() function returns 0 on success.
The current code was failing to detect the RAPL PMU
on real hardware  (missing /sys/devices/power) because
the return value of rdmsrl_safe() was misinterpreted.

Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Venkatesh Srinivas <venkateshs@google.com>
Cc: peterz@infradead.org
Cc: zheng.z.yan@intel.com
Link: http://lkml.kernel.org/r/20140423170418.GA12767@quad
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/perf_event_intel_rapl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 7c87424..619f769 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -543,7 +543,8 @@ static int rapl_cpu_prepare(int cpu)
 	if (phys_id < 0)
 		return -1;
 
-	if (!rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))
+	/* protect rdmsrl() to handle virtualization */
+	if (rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))
 		return -1;
 
 	pmu = kzalloc_node(sizeof(*pmu), GFP_KERNEL, cpu_to_node(cpu));