LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andi Kleen <ak@linux.intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Kan Liang <kan.liang@intel.com>, Jiri Olsa <jolsa@kernel.org>,
	David Carrillo-Cisneros <davidcc@google.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Tom Vaden <tom.vaden@hpe.com>
Subject: Re: [RFC] perf/x86/intel: Disable check_msr for real hw
Date: Fri, 21 Jun 2019 10:48:25 -0700	[thread overview]
Message-ID: <20190621174825.GA31027@tassilo.jf.intel.com> (raw)
In-Reply-To: <20190614112853.GC4325@krava>

On Fri, Jun 14, 2019 at 01:28:53PM +0200, Jiri Olsa wrote:
> hi,
> the HPE server can do POST tracing and have enabled LBR
> tracing during the boot, which makes check_msr fail falsly.
> 
> It looks like check_msr code was added only to check on guests
> MSR access, would it be then ok to disable check_msr for real
> hardware? (as in patch below)
> 
> We could also check if LBR tracing is enabled and make
> appropriate checks, but this change is simpler ;-)
> 
> ideas? thanks,
> jirka

Sorry for the late comment. I see this patch has been merged now.

Unfortunately I don't think it's a good idea. The problem 
is that the hypervisor flags are only set for a few hypervisors
that Linux knows about. But in practice there are many more
Hypervisors around that will not cause these flags to be set.
But these are still likely to miss MSRs.

The other hypervisors are relatively obscure, but eventually
someone will hit problems.

-Andi



  parent reply	other threads:[~2019-06-21 17:48 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 11:28 Jiri Olsa
2019-06-14 13:33 ` Peter Zijlstra
2019-06-14 13:45 ` Liang, Kan
2019-06-16 14:13   ` [PATCH] " Jiri Olsa
2019-06-16 20:56     ` Vaden, Tom (HPE Server OS Architecture)
2019-06-17 14:41     ` [tip:perf/core] perf/x86/intel: Disable check_msr for real HW tip-bot for Jiri Olsa
2019-06-21 17:48 ` Andi Kleen [this message]
2019-06-23 22:40   ` [RFC] perf/x86/intel: Disable check_msr for real hw Jiri Olsa
2019-06-23 23:44     ` Vaden, Tom (HPE Server OS Architecture)
2019-06-24  8:06     ` Paolo Bonzini
2019-06-24 16:46     ` Andi Kleen
2019-06-24 18:06       ` Jiri Olsa
2019-06-24 18:38         ` Andi Kleen
2019-06-24 18:49           ` Jiri Olsa

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190621174825.GA31027@tassilo.jf.intel.com \
    --to=ak@linux.intel.com \
    --cc=acme@kernel.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=davidcc@google.com \
    --cc=jolsa@kernel.org \
    --cc=jolsa@redhat.com \
    --cc=kan.liang@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=namhyung@kernel.org \
    --cc=peterz@infradead.org \
    --cc=tom.vaden@hpe.com \
    --subject='Re: [RFC] perf/x86/intel: Disable check_msr for real hw' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).