linux-kernel - Re: [RFC][PATCH] perf, intel: Don't touch MSR_IA32

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]

Message-ID: <1347475934.15764.90.camel@twins>
Date:	Wed, 12 Sep 2012 20:52:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Oleg Nesterov <oleg@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC][PATCH] perf, intel: Don't touch MSR_IA32_DEBUGCTLMSR from
 NMI context

On Wed, 2012-09-12 at 20:50 +0200, Stephane Eranian wrote:

> > As for BTS, it looks like we don't throttle the thing at all, so we
> > shouldn't ever get to the asymmetric thing, right?
> No you do, in the same function:
> static void intel_pmu_disable_event(struct perf_event *event)
> {
>         struct hw_perf_event *hwc = &event->hw;
>         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> 
>         if (unlikely(hwc->idx == INTEL_PMC_IDX_FIXED_BTS)) {
>                 intel_pmu_disable_bts();
>                 intel_pmu_drain_bts_buffer();
>                 return;
>         }

Right, but the main event loop in intel_pmu_handle_irq() is over the
MSR_CORE_PERF_GLOBAL_STATUS status bits, BTS is not included in those,
so we'd never end up calling x86_pmu_stop() on the associated event.
--
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/