Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Stephane Eranian wrote:
> On Sun, Oct 21, 2012 at 8:03 PM, Ingo Molnar wrote:
> >
> > * Stephane Eranian wrote:
> >
> >> On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar wrote:
> >> >
> >> > * Andi Kleen wrote:
> >> >
> >> >> > > > This isn't limited to admin, right? So the above turns into a DoS
> >> >> > > > on the
> >> >> > > > console.
> >> >> > > >
> >> >> > > Ok, so how about a WARN_ON_ONCE() instead?
> >> >> >
> >> >> > That should be fine I guess ;-)
> >> >>
> >> >> imho there is need for a generic mechanism to return an error
> >> >> string to the user program without such hacks.
> >> >
> >> > Agreed - we could return an 'extended errno' long error return
> >> > value, which in reality is a pointer to an error string (in
> >> > perf_attr::error_str), and copy that string to user-space at
> >> > perf syscall return time.
> >> >
> >> I assume by perf_attr:error_str, you actually mean:
> >>
> >> struct perf_event_attr {
> >>char error_str[PERF_ERR_LEN];
> >> };
> >>
> >> Right?
> >
> > I don't think we should allocate space in the attr, instead we
> > should use something like:
> >
> > u8 __user *err_str;
> > u32 err_str_len;
> >
> > which would be filled in by tooling with a string and a max_len
> > value, and strncpy_to_user() could do the rest on the kernel
> > side. [ A minor complication is that we don't have a
> > strncpy_to_user() method at the moment. ]
> >
> > Static strings could be handled this way.
> >
> > [ Dynamic strings could be supported too with a few tricks,
> > although I doubt it matters in practice. ]
> >
>
> Ok, but this still limits returning error string to the
> perf_event_open() syscall, not read(), ioctl() and such.
Yes - but this should be enough to handle most of the cases in
practice - because the richness of the various perf components
is mostly exposed via the perf syscall. By the time we get to
read() and ioctl() we are in a pretty well defined domain.
Also, I don't think people want the (small but nonzero) overhead
of extended error reporting for read or ioctl.
> I am fine with this change. However, I think it should be
> added separately from my inst_retired:prec_dist patch. It has
> a broader impact.
Most definitely.
Thanks,
Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Stephane Eranian eran...@google.com wrote:
On Sun, Oct 21, 2012 at 8:03 PM, Ingo Molnar mi...@kernel.org wrote:
* Stephane Eranian eran...@google.com wrote:
On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar mi...@kernel.org wrote:
* Andi Kleen a...@linux.intel.com wrote:
This isn't limited to admin, right? So the above turns into a DoS
on the
console.
Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
imho there is need for a generic mechanism to return an error
string to the user program without such hacks.
Agreed - we could return an 'extended errno' long error return
value, which in reality is a pointer to an error string (in
perf_attr::error_str), and copy that string to user-space at
perf syscall return time.
I assume by perf_attr:error_str, you actually mean:
struct perf_event_attr {
char error_str[PERF_ERR_LEN];
};
Right?
I don't think we should allocate space in the attr, instead we
should use something like:
u8 __user *err_str;
u32 err_str_len;
which would be filled in by tooling with a string and a max_len
value, and strncpy_to_user() could do the rest on the kernel
side. [ A minor complication is that we don't have a
strncpy_to_user() method at the moment. ]
Static strings could be handled this way.
[ Dynamic strings could be supported too with a few tricks,
although I doubt it matters in practice. ]
Ok, but this still limits returning error string to the
perf_event_open() syscall, not read(), ioctl() and such.
Yes - but this should be enough to handle most of the cases in
practice - because the richness of the various perf components
is mostly exposed via the perf syscall. By the time we get to
read() and ioctl() we are in a pretty well defined domain.
Also, I don't think people want the (small but nonzero) overhead
of extended error reporting for read or ioctl.
I am fine with this change. However, I think it should be
added separately from my inst_retired:prec_dist patch. It has
a broader impact.
Most definitely.
Thanks,
Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Sun, Oct 21, 2012 at 8:03 PM, Ingo Molnar wrote:
>
> * Stephane Eranian wrote:
>
>> On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar wrote:
>> >
>> > * Andi Kleen wrote:
>> >
>> >> > > > This isn't limited to admin, right? So the above turns into a DoS
>> >> > > > on the
>> >> > > > console.
>> >> > > >
>> >> > > Ok, so how about a WARN_ON_ONCE() instead?
>> >> >
>> >> > That should be fine I guess ;-)
>> >>
>> >> imho there is need for a generic mechanism to return an error
>> >> string to the user program without such hacks.
>> >
>> > Agreed - we could return an 'extended errno' long error return
>> > value, which in reality is a pointer to an error string (in
>> > perf_attr::error_str), and copy that string to user-space at
>> > perf syscall return time.
>> >
>> I assume by perf_attr:error_str, you actually mean:
>>
>> struct perf_event_attr {
>>char error_str[PERF_ERR_LEN];
>> };
>>
>> Right?
>
> I don't think we should allocate space in the attr, instead we
> should use something like:
>
> u8 __user *err_str;
> u32 err_str_len;
>
> which would be filled in by tooling with a string and a max_len
> value, and strncpy_to_user() could do the rest on the kernel
> side. [ A minor complication is that we don't have a
> strncpy_to_user() method at the moment. ]
>
> Static strings could be handled this way.
>
> [ Dynamic strings could be supported too with a few tricks,
> although I doubt it matters in practice. ]
>
Ok, but this still limits returning error string to the perf_event_open()
syscall, not read(), ioctl() and such.
I am fine with this change. However, I think it should be added separately
from my inst_retired:prec_dist patch. It has a broader impact.
>> > Thus error-string aware tooling could print the error string.
>> >
>> > So PMU drivers could do something obvious like:
>> >
>> > return (long)"perf: INST_RETIRED.PREC_DIST only works in exclusive
>> > mode";
>> >
>> > The perf syscall notices these pointers by noticing that the
>> > error code returned is outside the errno range.
>>
>> Is that always the case on all archs?
>
> I think yes - and if not then it can be solved via some trivial
> offset value added to it on such an architecture, without
> complicating the code on normal architectures.
>
> Thanks,
>
> Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Sun, Oct 21, 2012 at 8:03 PM, Ingo Molnar mi...@kernel.org wrote:
* Stephane Eranian eran...@google.com wrote:
On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar mi...@kernel.org wrote:
* Andi Kleen a...@linux.intel.com wrote:
This isn't limited to admin, right? So the above turns into a DoS
on the
console.
Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
imho there is need for a generic mechanism to return an error
string to the user program without such hacks.
Agreed - we could return an 'extended errno' long error return
value, which in reality is a pointer to an error string (in
perf_attr::error_str), and copy that string to user-space at
perf syscall return time.
I assume by perf_attr:error_str, you actually mean:
struct perf_event_attr {
char error_str[PERF_ERR_LEN];
};
Right?
I don't think we should allocate space in the attr, instead we
should use something like:
u8 __user *err_str;
u32 err_str_len;
which would be filled in by tooling with a string and a max_len
value, and strncpy_to_user() could do the rest on the kernel
side. [ A minor complication is that we don't have a
strncpy_to_user() method at the moment. ]
Static strings could be handled this way.
[ Dynamic strings could be supported too with a few tricks,
although I doubt it matters in practice. ]
Ok, but this still limits returning error string to the perf_event_open()
syscall, not read(), ioctl() and such.
I am fine with this change. However, I think it should be added separately
from my inst_retired:prec_dist patch. It has a broader impact.
Thus error-string aware tooling could print the error string.
So PMU drivers could do something obvious like:
return (long)perf: INST_RETIRED.PREC_DIST only works in exclusive
mode;
The perf syscall notices these pointers by noticing that the
error code returned is outside the errno range.
Is that always the case on all archs?
I think yes - and if not then it can be solved via some trivial
offset value added to it on such an architecture, without
complicating the code on normal architectures.
Thanks,
Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Stephane Eranian wrote:
> On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar wrote:
> >
> > * Andi Kleen wrote:
> >
> >> > > > This isn't limited to admin, right? So the above turns into a DoS on
> >> > > > the
> >> > > > console.
> >> > > >
> >> > > Ok, so how about a WARN_ON_ONCE() instead?
> >> >
> >> > That should be fine I guess ;-)
> >>
> >> imho there is need for a generic mechanism to return an error
> >> string to the user program without such hacks.
> >
> > Agreed - we could return an 'extended errno' long error return
> > value, which in reality is a pointer to an error string (in
> > perf_attr::error_str), and copy that string to user-space at
> > perf syscall return time.
> >
> I assume by perf_attr:error_str, you actually mean:
>
> struct perf_event_attr {
>char error_str[PERF_ERR_LEN];
> };
>
> Right?
I don't think we should allocate space in the attr, instead we
should use something like:
u8 __user *err_str;
u32 err_str_len;
which would be filled in by tooling with a string and a max_len
value, and strncpy_to_user() could do the rest on the kernel
side. [ A minor complication is that we don't have a
strncpy_to_user() method at the moment. ]
Static strings could be handled this way.
[ Dynamic strings could be supported too with a few tricks,
although I doubt it matters in practice. ]
> > Thus error-string aware tooling could print the error string.
> >
> > So PMU drivers could do something obvious like:
> >
> > return (long)"perf: INST_RETIRED.PREC_DIST only works in exclusive
> > mode";
> >
> > The perf syscall notices these pointers by noticing that the
> > error code returned is outside the errno range.
>
> Is that always the case on all archs?
I think yes - and if not then it can be solved via some trivial
offset value added to it on such an architecture, without
complicating the code on normal architectures.
Thanks,
Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar wrote:
>
> * Andi Kleen wrote:
>
>> > > > This isn't limited to admin, right? So the above turns into a DoS on
>> > > > the
>> > > > console.
>> > > >
>> > > Ok, so how about a WARN_ON_ONCE() instead?
>> >
>> > That should be fine I guess ;-)
>>
>> imho there is need for a generic mechanism to return an error
>> string to the user program without such hacks.
>
> Agreed - we could return an 'extended errno' long error return
> value, which in reality is a pointer to an error string (in
> perf_attr::error_str), and copy that string to user-space at
> perf syscall return time.
>
I assume by perf_attr:error_str, you actually mean:
struct perf_event_attr {
char error_str[PERF_ERR_LEN];
};
Right?
> Thus error-string aware tooling could print the error string.
>
> So PMU drivers could do something obvious like:
>
> return (long)"perf: INST_RETIRED.PREC_DIST only works in exclusive
> mode";
>
> The perf syscall notices these pointers by noticing that the
> error code returned is outside the errno range.
>
Is that always the case on all archs?
> Old userspace will get a -EINVAL and no string copied into the
> error string buffer.
>
> New userspace would get the error string copied into
> perf_attr::error_str, plus a 'normal' -EINVAL error code.
>
> The only cost on the kernel side is to make sure all "string
> errors" are returned as long.
>
> Thanks,
>
> Ingo
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Andi Kleen wrote: > > > > This isn't limited to admin, right? So the above turns into a DoS on the > > > > console. > > > > > > > Ok, so how about a WARN_ON_ONCE() instead? > > > > That should be fine I guess ;-) > > imho there is need for a generic mechanism to return an error > string to the user program without such hacks. Agreed - we could return an 'extended errno' long error return value, which in reality is a pointer to an error string (in perf_attr::error_str), and copy that string to user-space at perf syscall return time. Thus error-string aware tooling could print the error string. So PMU drivers could do something obvious like: return (long)"perf: INST_RETIRED.PREC_DIST only works in exclusive mode"; The perf syscall notices these pointers by noticing that the error code returned is outside the errno range. Old userspace will get a -EINVAL and no string copied into the error string buffer. New userspace would get the error string copied into perf_attr::error_str, plus a 'normal' -EINVAL error code. The only cost on the kernel side is to make sure all "string errors" are returned as long. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Andi Kleen a...@linux.intel.com wrote: This isn't limited to admin, right? So the above turns into a DoS on the console. Ok, so how about a WARN_ON_ONCE() instead? That should be fine I guess ;-) imho there is need for a generic mechanism to return an error string to the user program without such hacks. Agreed - we could return an 'extended errno' long error return value, which in reality is a pointer to an error string (in perf_attr::error_str), and copy that string to user-space at perf syscall return time. Thus error-string aware tooling could print the error string. So PMU drivers could do something obvious like: return (long)perf: INST_RETIRED.PREC_DIST only works in exclusive mode; The perf syscall notices these pointers by noticing that the error code returned is outside the errno range. Old userspace will get a -EINVAL and no string copied into the error string buffer. New userspace would get the error string copied into perf_attr::error_str, plus a 'normal' -EINVAL error code. The only cost on the kernel side is to make sure all string errors are returned as long. Thanks, Ingo -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar mi...@kernel.org wrote:
* Andi Kleen a...@linux.intel.com wrote:
This isn't limited to admin, right? So the above turns into a DoS on
the
console.
Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
imho there is need for a generic mechanism to return an error
string to the user program without such hacks.
Agreed - we could return an 'extended errno' long error return
value, which in reality is a pointer to an error string (in
perf_attr::error_str), and copy that string to user-space at
perf syscall return time.
I assume by perf_attr:error_str, you actually mean:
struct perf_event_attr {
char error_str[PERF_ERR_LEN];
};
Right?
Thus error-string aware tooling could print the error string.
So PMU drivers could do something obvious like:
return (long)perf: INST_RETIRED.PREC_DIST only works in exclusive
mode;
The perf syscall notices these pointers by noticing that the
error code returned is outside the errno range.
Is that always the case on all archs?
Old userspace will get a -EINVAL and no string copied into the
error string buffer.
New userspace would get the error string copied into
perf_attr::error_str, plus a 'normal' -EINVAL error code.
The only cost on the kernel side is to make sure all string
errors are returned as long.
Thanks,
Ingo
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
* Stephane Eranian eran...@google.com wrote:
On Sun, Oct 21, 2012 at 6:55 PM, Ingo Molnar mi...@kernel.org wrote:
* Andi Kleen a...@linux.intel.com wrote:
This isn't limited to admin, right? So the above turns into a DoS on
the
console.
Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
imho there is need for a generic mechanism to return an error
string to the user program without such hacks.
Agreed - we could return an 'extended errno' long error return
value, which in reality is a pointer to an error string (in
perf_attr::error_str), and copy that string to user-space at
perf syscall return time.
I assume by perf_attr:error_str, you actually mean:
struct perf_event_attr {
char error_str[PERF_ERR_LEN];
};
Right?
I don't think we should allocate space in the attr, instead we
should use something like:
u8 __user *err_str;
u32 err_str_len;
which would be filled in by tooling with a string and a max_len
value, and strncpy_to_user() could do the rest on the kernel
side. [ A minor complication is that we don't have a
strncpy_to_user() method at the moment. ]
Static strings could be handled this way.
[ Dynamic strings could be supported too with a few tricks,
although I doubt it matters in practice. ]
Thus error-string aware tooling could print the error string.
So PMU drivers could do something obvious like:
return (long)perf: INST_RETIRED.PREC_DIST only works in exclusive
mode;
The perf syscall notices these pointers by noticing that the
error code returned is outside the errno range.
Is that always the case on all archs?
I think yes - and if not then it can be solved via some trivial
offset value added to it on such an architecture, without
complicating the code on normal architectures.
Thanks,
Ingo
--
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
> > > This isn't limited to admin, right? So the above turns into a DoS on the > > > console. > > > > > Ok, so how about a WARN_ON_ONCE() instead? > > That should be fine I guess ;-) imho there is need for a generic mechanism to return an error string to the user program without such hacks. -Andi -- a...@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, 2012-10-19 at 18:31 +0200, Stephane Eranian wrote:
> On Fri, Oct 19, 2012 at 6:27 PM, Peter Zijlstra wrote:
> > On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
> >> +static int intel_pebs_aliases_snb(struct perf_event *event)
> >> +{
> >> + u64 cfg = event->hw.config;
> >> + /*
> >> +* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
> >> +* be measured alone on SNB (exclusive PMU access) as per Intel
> >> SDM.
> >> +*/
> >> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 &&
> >> !event->attr.exclusive) {
> >> + pr_info("perf: INST_RETIRED.PREC_DIST only works in
> >> exclusive mode\n");
> >> + return -EINVAL;
> >
> > This isn't limited to admin, right? So the above turns into a DoS on the
> > console.
> >
> Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, Oct 19, 2012 at 6:27 PM, Peter Zijlstra wrote:
> On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
>> +static int intel_pebs_aliases_snb(struct perf_event *event)
>> +{
>> + u64 cfg = event->hw.config;
>> + /*
>> +* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
>> +* be measured alone on SNB (exclusive PMU access) as per Intel SDM.
>> +*/
>> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 &&
>> !event->attr.exclusive) {
>> + pr_info("perf: INST_RETIRED.PREC_DIST only works in
>> exclusive mode\n");
>> + return -EINVAL;
>
> This isn't limited to admin, right? So the above turns into a DoS on the
> console.
>
Ok, so how about a WARN_ON_ONCE() instead?
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
> +static int intel_pebs_aliases_snb(struct perf_event *event)
> +{
> + u64 cfg = event->hw.config;
> + /*
> +* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
> +* be measured alone on SNB (exclusive PMU access) as per Intel SDM.
> +*/
> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 &&
> !event->attr.exclusive) {
> + pr_info("perf: INST_RETIRED.PREC_DIST only works in exclusive
> mode\n");
> + return -EINVAL;
This isn't limited to admin, right? So the above turns into a DoS on the
console.
> + }
> +
> + return intel_pebs_aliases_ivb(event);
> }
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, Oct 19, 2012 at 5:49 PM, Andi Kleen wrote:
>> + /*
>> + * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
>> + * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
>> + */
>> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 && !event->attr.exclusive)
>> {
>> + pr_info("perf: INST_RETIRED.PREC_DIST only works in exclusive
>> mode\n");
>> + return -EINVAL;
>> + }
>
>
> Strictly you have to check for precise too, right?
>
Yes, the restriction is enforced only when PEBS is active and
this is what I do based on where pebs_aliases() is called.
> -Andi
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
> + /*
> + * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
> + * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
> + */
> + if ((cfg & INTEL_ARCH_EVENT_MASK) == 0x01c0 && !event->attr.exclusive) {
> + pr_info("perf: INST_RETIRED.PREC_DIST only works in exclusive
> mode\n");
> + return -EINVAL;
> + }
Strictly you have to check for precise too, right?
-Andi
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
+ /*
+ * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
+ * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
+ */
+ if ((cfg INTEL_ARCH_EVENT_MASK) == 0x01c0 !event-attr.exclusive) {
+ pr_info(perf: INST_RETIRED.PREC_DIST only works in exclusive
mode\n);
+ return -EINVAL;
+ }
Strictly you have to check for precise too, right?
-Andi
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, Oct 19, 2012 at 5:49 PM, Andi Kleen a...@linux.intel.com wrote:
+ /*
+ * for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
+ * be measured alone on SNB (exclusive PMU access) as per Intel SDM.
+ */
+ if ((cfg INTEL_ARCH_EVENT_MASK) == 0x01c0 !event-attr.exclusive)
{
+ pr_info(perf: INST_RETIRED.PREC_DIST only works in exclusive
mode\n);
+ return -EINVAL;
+ }
Strictly you have to check for precise too, right?
Yes, the restriction is enforced only when PEBS is active and
this is what I do based on where pebs_aliases() is called.
-Andi
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
+static int intel_pebs_aliases_snb(struct perf_event *event)
+{
+ u64 cfg = event-hw.config;
+ /*
+* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
+* be measured alone on SNB (exclusive PMU access) as per Intel SDM.
+*/
+ if ((cfg INTEL_ARCH_EVENT_MASK) == 0x01c0
!event-attr.exclusive) {
+ pr_info(perf: INST_RETIRED.PREC_DIST only works in exclusive
mode\n);
+ return -EINVAL;
This isn't limited to admin, right? So the above turns into a DoS on the
console.
+ }
+
+ return intel_pebs_aliases_ivb(event);
}
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, Oct 19, 2012 at 6:27 PM, Peter Zijlstra pet...@infradead.org wrote:
On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
+static int intel_pebs_aliases_snb(struct perf_event *event)
+{
+ u64 cfg = event-hw.config;
+ /*
+* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
+* be measured alone on SNB (exclusive PMU access) as per Intel SDM.
+*/
+ if ((cfg INTEL_ARCH_EVENT_MASK) == 0x01c0
!event-attr.exclusive) {
+ pr_info(perf: INST_RETIRED.PREC_DIST only works in
exclusive mode\n);
+ return -EINVAL;
This isn't limited to admin, right? So the above turns into a DoS on the
console.
Ok, so how about a WARN_ON_ONCE() instead?
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
On Fri, 2012-10-19 at 18:31 +0200, Stephane Eranian wrote:
On Fri, Oct 19, 2012 at 6:27 PM, Peter Zijlstra pet...@infradead.org wrote:
On Fri, 2012-10-19 at 16:52 +0200, Stephane Eranian wrote:
+static int intel_pebs_aliases_snb(struct perf_event *event)
+{
+ u64 cfg = event-hw.config;
+ /*
+* for INST_RETIRED.PREC_DIST to work correctly with PEBS, it must
+* be measured alone on SNB (exclusive PMU access) as per Intel
SDM.
+*/
+ if ((cfg INTEL_ARCH_EVENT_MASK) == 0x01c0
!event-attr.exclusive) {
+ pr_info(perf: INST_RETIRED.PREC_DIST only works in
exclusive mode\n);
+ return -EINVAL;
This isn't limited to admin, right? So the above turns into a DoS on the
console.
Ok, so how about a WARN_ON_ONCE() instead?
That should be fine I guess ;-)
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Re: [PATCH 2/2] perf: SNB exclusive PMU access for INST_RETIRED:PREC_DIST
This isn't limited to admin, right? So the above turns into a DoS on the console. Ok, so how about a WARN_ON_ONCE() instead? That should be fine I guess ;-) imho there is need for a generic mechanism to return an error string to the user program without such hacks. -Andi -- a...@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
