linux-kernel - [tip:perf/urgent] perf tool: Precise mode requires 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>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-1342798cc13e3b48d9b5738f0c8fa812ccea8101@git.kernel.org>
Date:	Fri, 19 Oct 2012 17:55:38 -0700
From:	tip-bot for David Ahern <dsahern@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, hpa@...or.com,
	mingo@...nel.org, peterz@...radead.org, gleb@...hat.com,
	robert.richter@....com, dsahern@...il.com, tglx@...utronix.de,
	avi@...hat.com
Subject: [tip:perf/urgent] perf tool: Precise mode requires exclude_guest

Commit-ID:  1342798cc13e3b48d9b5738f0c8fa812ccea8101
Gitweb:     http://git.kernel.org/tip/1342798cc13e3b48d9b5738f0c8fa812ccea8101
Author:     David Ahern <dsahern@...il.com>
AuthorDate: Thu, 13 Sep 2012 14:59:13 -0600
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 16 Oct 2012 12:43:31 -0300

perf tool: Precise mode requires exclude_guest

Summary of events per Peter:

  "Intel PEBS in VT-x context uses the DS address as a guest linear address,
  even though its programmed by the host as a host linear address. This
  either results in guest memory corruption and or the hardware faulting and
  'crashing' the virtual machine.  Therefore we have to disable PEBS on VT-x
  enter and re-enable on VT-x exit, enforcing a strict exclude_guest.

  AMB IBS does work but doesn't currently support exclude_* at all,
  setting an exclude_* bit will make it fail."

This patch handles userspace perf command, setting the exclude_guest
attribute if precise mode is requested, but only if a user has not
specified a request for guest or host only profiling (G or H attribute).

Kernel side AMD currently ignores all exclude_* bits, so there is no impact
to existing IBS code paths. Robert Richter has a patch where IBS code will
return EINVAL if an exclude_* bit is set. When this goes in it means use
of :p on AMD with IBS will first fail with EINVAL (because exclude_guest
will be set). Then the existing fallback code within perf will unset
exclude_guest and try again. The second attempt will succeed if the CPU
supports IBS profiling.

Signed-off-by: David Ahern <dsahern@...il.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Acked-by: Robert Richter <robert.richter@....com>
Tested-by: Robert Richter <robert.richter@....com>
Reviewed-by: Robert Richter <robert.richter@....com>
Cc: Avi Kivity <avi@...hat.com>
Cc: Gleb Natapov <gleb@...hat.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Robert Richter <robert.richter@....com>
Link: http://lkml.kernel.org/r/1347569955-54626-2-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/parse-events.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index aed38e4..75c7b0f 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -690,6 +690,9 @@ static int get_event_modifier(struct event_modifier *mod, char *str,
 			eH = 0;
 		} else if (*str == 'p') {
 			precise++;
+			/* use of precise requires exclude_guest */
+			if (!exclude_GH)
+				eG = 1;
 		} else
 			break;

--
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/