linux-kernel - Re: [RFC/PATCH 0/4] perf tools: Do not set attr.exclude

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>] [day] [month] [year] [list]

Message-ID: <20240903083933.GQ4723@noisy.programming.kicks-ass.net>
Date: Tue, 3 Sep 2024 10:39:33 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	Ravi Bangoria <ravi.bangoria@....com>,
	Mark Rutland <mark.rutland@....com>,
	James Clark <james.clark@....com>,
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
	Kajol Jain <kjain@...ux.ibm.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	Atish Patra <atishp@...shpatra.org>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Mingwei Zhang <mizhang@...gle.com>
Subject: Re: [RFC/PATCH 0/4] perf tools: Do not set attr.exclude_guest by
 default (v1)

On Mon, Sep 02, 2024 at 10:20:41AM -0700, Namhyung Kim wrote:
> Hi Peter,
> 
> On Mon, Sep 2, 2024 at 1:56 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Sun, Sep 01, 2024 at 06:46:17PM -0700, Namhyung Kim wrote:
> > > Hello,
> > >
> > > I found perf tools set exclude_guest bit inconsistently.  It used to
> > > set the bit but now the default event for perf record doesn't.  So I'm
> > > wondering why we want the bit in the first place.
> > >
> > > Actually it's not good for PMUs don't support any exclusion like AMD
> > > IBS because it disables new features after the exclude_guest due to
> > > the missing feature detection logic.
> > >
> > > AFAIK it doesn't matter for the most cases but perf kvm.  If users
> > > need to set the bit, they can still use :H modifier.  Please let me
> > > know if it's ok for you.
> >
> > IIRc the point of setting exclude_guest by default was so that default
> > perf keeps working in the precense of that PMU pass through mess, no?
> 
> Sorry I haven't followed the vPMU pass through threads.  It makes
> sense to keep the exclude_guest for the kernels with it.  But I guess
> it's configurable via kernel config and/or boot option.

Yeah, you need KVM build with the passthrough thing on, and then at
runtime enable it or something -- I too have to still read the latest
posting.

> A question, with PMU pass through would the kernel reject host events
> which don't set the exclude_guest?

Yes.