linux-kernel - Re: [BUG/RFC] perf test fails on AMD CPUs

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Date:	Wed, 19 Aug 2015 17:58:17 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Andy Lutomirski <luto@...capital.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Robert Richter <rric@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Jan Stancek <jstancek@...hat.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Sherry Hurwitz <sherry.hurwitz@....com>
Subject: Re: [BUG/RFC] perf test fails on AMD CPUs

On Wed, Aug 19, 2015 at 05:47:00PM +0200, Borislav Petkov wrote:
> On Wed, Aug 19, 2015 at 10:55:46AM +0200, Jiri Olsa wrote:
> > this is the perf breakpoint address:
> >   000000000045b260 <test_function>:
> > 
> > this is trace_printk output for NEW microcode 0x6000832:
> > 
> > DEBUG EX
> >             perf-893   [003] d...  1358.053633: sync_regs: sync_regs eregs ffff88012ecc7f58, regs ffff8800c9f1bf58
> >             perf-893   [003] d...  1358.053635: do_debug: do_debug-1 regs ffff8800c9f1bf58, eflags 217, rip 45b260
> >             perf-893   [003] d.h.  1358.053641: do_debug: do_debug-2 eflags 10217, rip 45b260
> >             perf-893   [003] d...  1358.053642: prepare_exit_to_usermode: prepare_exit_to_usermode1 regs ffff8800c9f1bf58, eflags 10217, rip 45b260
> >             perf-893   [003] d...  1358.053643: prepare_exit_to_usermode: prepare_exit_to_usermode3 regs ffff8800c9f1bf58, eflags 10217, rip 45b260
> 
> Yikes!
> 
> Something cleared EFLAGS.RF here. And the same thing doesn't happen with
> the older ucode version. Are you sure nothing happens in-between
> prepare_exit_to_usermode() and smp_irq_work_interrupt()?

if anything happens there, I dont see it ;-)

I was told RHEL7 went off and on several times with AMD microcode,
now it's the period we actually install it.. I'll poke around to see
who made that decissions, he/she might know more ;-)

jirka
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