From: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
Jerry Hoemann <jerry.hoemann@hpe.com>
Subject: Re: [PATCH] perf/x86/amd: Change NMI latency mitigation to use a timestamp
Date: Fri, 2 Aug 2019 14:33:41 +0000 [thread overview]
Message-ID: <925c3458-aeae-a44b-ddd5-40a1e173a307@amd.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908012352390.1789@nanos.tec.linutronix.de>
On 8/1/19 4:59 PM, Thomas Gleixner wrote:
> On Thu, 1 Aug 2019, Peter Zijlstra wrote:
>> On Thu, Aug 01, 2019 at 11:34:23PM +0200, Thomas Gleixner wrote:
>>> Avoid the whole NMI mess, make the PMC interrupt a proper vector in the
>>> highest prio bucket and instead of using CLI/STI use CR8. That would have
>>> the additional advantage that we could prevent perf "NMI" then occsionally :)
>>
>> Exactly, and not only the PMC, we can basically start giving out actual
>> vectors on register_nmi_handler() and do away with all that shared line
>> crap.
>>
>> And then the actual NMI line will be mostly empty again, and it can read
>> its stupid slow reason port again.
>>
>> One complication though; IRET et al only do EFLAGS, not CR8, so that's
>> going to be massive fun :-(
Talking to the hardware folks, they say setting CR8 is a serializing
instruction and has to communicate out to the APIC, so it's better to
use CLI/STI.
Thanks,
Tom
>>
>> Did I say I hates the x86 interrupt scheme?
>
> You're not alone.
>
> That stuff definitely violates article 3 of the Convention for the
> Protection of Human Rights and Fundamental Freedoms.
>
>
next prev parent reply other threads:[~2019-08-02 14:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-01 18:57 [PATCH] perf/x86/amd: Change NMI latency mitigation to use a timestamp Lendacky, Thomas
2019-08-01 21:16 ` Peter Zijlstra
2019-08-01 21:29 ` Lendacky, Thomas
2019-08-01 21:34 ` Thomas Gleixner
2019-08-01 21:48 ` Peter Zijlstra
2019-08-01 21:59 ` Thomas Gleixner
2019-08-02 14:33 ` Lendacky, Thomas [this message]
2019-08-02 16:20 ` Peter Zijlstra
2019-08-02 16:33 ` Peter Zijlstra
2019-08-08 20:33 ` Jerry Hoemann
2019-09-13 19:52 ` Jerry Hoemann
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