linux-kernel - Re: [PATCH 1/2] perf/core: Adding capability to disable PMUs event multiplexing

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: <20191106094032.GV4131@hirez.programming.kicks-ass.net>
Date:   Wed, 6 Nov 2019 10:40:32 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ganapatrao Prabhakerrao Kulkarni <gkulkarni@...vell.com>
Cc:     "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "will@...nel.org" <will@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "corbet@....net" <corbet@....net>,
        "gklkml16@...il.com" <gklkml16@...il.com>
Subject: Re: [PATCH 1/2] perf/core: Adding capability to disable PMUs event
 multiplexing

On Wed, Nov 06, 2019 at 01:01:40AM +0000, Ganapatrao Prabhakerrao Kulkarni wrote:
> When PMUs are registered, perf core enables event multiplexing
> support by default. There is no provision for PMUs to disable
> event multiplexing, if PMUs want to disable due to unavoidable
> circumstances like hardware errata etc.
> 
> Adding PMU capability flag PERF_PMU_CAP_NO_MUX_EVENTS and support
> to allow PMUs to explicitly disable event multiplexing.

This doesn't make sense, multiplexing relies on nothing that normal
event scheduling doesn't also rely on.

Either you can schedule different sets of events, or you cannot.

NAK.