* [PATCH] RDMSR before test_cpu_capacity brings about KVM warning
@ 2015-08-14 10:07 Huaitong Han
2015-08-17 12:04 ` Alexander Shishkin
0 siblings, 1 reply; 3+ messages in thread
From: Huaitong Han @ 2015-08-14 10:07 UTC (permalink / raw)
To: alexander.shishkin, mingo, acme; +Cc: linux-kernel, Huaitong Han
rdmsrl_safe does not lead to #GP in native kernel although CPU
does not support INTEL_PT, but if KVM does not support INTEL_PT,
the codes cannot understand MSR_IA32_RTIT_CTL, and the warning
is produced.
If KVM does not support INTEL_PT, its guest CPUID also does not.
So test_cpu_cap is added before RDMSR, and it is more in line with
the code style.
Signed-off-by: Huaitong Han <huaitong.han@intel.com>
diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 183de71..4cc6492 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -123,9 +123,6 @@ static int __init pt_pmu_hw_init(void)
long i;
attrs = NULL;
- ret = -ENODEV;
- if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT))
- goto fail;
for (i = 0; i < PT_CPUID_LEAVES; i++) {
cpuid_count(20, i,
@@ -1061,6 +1058,10 @@ static __init int pt_init(void)
int ret, cpu, prior_warn = 0;
BUILD_BUG_ON(sizeof(struct topa) > PAGE_SIZE);
+
+ if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT))
+ return -ENODEV;
+
get_online_cpus();
for_each_online_cpu(cpu) {
u64 ctl;
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] RDMSR before test_cpu_capacity brings about KVM warning
2015-08-14 10:07 [PATCH] RDMSR before test_cpu_capacity brings about KVM warning Huaitong Han
@ 2015-08-17 12:04 ` Alexander Shishkin
2015-08-17 13:23 ` Han, Huaitong
0 siblings, 1 reply; 3+ messages in thread
From: Alexander Shishkin @ 2015-08-17 12:04 UTC (permalink / raw)
To: Huaitong Han; +Cc: linux-kernel, Huaitong Han, Peter Zijlstra, mingo, acme
Huaitong Han <huaitong.han@intel.com> writes:
> rdmsrl_safe does not lead to #GP in native kernel although CPU
> does not support INTEL_PT, but if KVM does not support INTEL_PT,
> the codes cannot understand MSR_IA32_RTIT_CTL, and the warning
> is produced.
"the codes"?
> If KVM does not support INTEL_PT, its guest CPUID also does not.
> So test_cpu_cap is added before RDMSR, and it is more in line with
> the code style.
It does make more sense like this, but please improve this commit
message. And don't forget to include Peter in the loop.
FWIW,
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Regards,
--
Alex
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] RDMSR before test_cpu_capacity brings about KVM warning
2015-08-17 12:04 ` Alexander Shishkin
@ 2015-08-17 13:23 ` Han, Huaitong
0 siblings, 0 replies; 3+ messages in thread
From: Han, Huaitong @ 2015-08-17 13:23 UTC (permalink / raw)
To: alexander.shishkin; +Cc: linux-kernel, a.p.zijlstra, mingo, acme
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 1137 bytes --]
On Mon, 2015-08-17 at 15:04 +0300, Alexander Shishkin wrote:
> Huaitong Han <huaitong.han@intel.com> writes:
>
> > rdmsrl_safe does not lead to #GP in native kernel although CPU
> > does not support INTEL_PT, but if KVM does not support INTEL_PT,
> > the codes cannot understand MSR_IA32_RTIT_CTL, and the warning
> > is produced.
>
> "the codes"?
KVM codes. Current KVM does not support Intel_PT. But guest kernel may
readmsr MSR_IA32_RTIT_CTL that KVM cannot understand.
Details from https://bugzilla.kernel.org/show_bug.cgi?id=102651
>
> > If KVM does not support INTEL_PT, its guest CPUID also does not.
> > So test_cpu_cap is added before RDMSR, and it is more in line with
> > the code style.
>
> It does make more sense like this, but please improve this commit
> message. And don't forget to include Peter in the loop.
I will update the commit message.
>
> FWIW,
>
> Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
>
> Regards,
> --
> Alex
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^ permalink raw reply [flat|nested] 3+ messages in thread
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