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

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Date:	Wed, 19 Aug 2015 17:47:00 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Jiri Olsa <jolsa@...hat.com>
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 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()?

It looks like nothing does because the timestamps are really close.

> WORK_IRQ
>  --->       perf-893   [003] d...  1358.053645: smp_irq_work_interrupt: smp_irq_work_interrupt1 regs ffff8800c9f1bf58, eflags 217, rip 45b260
>             perf-893   [003] d.h.  1358.053650: perf_event_wakeup: irq_work SIGIO
>             perf-893   [003] d...  1358.053651: smp_irq_work_interrupt: smp_irq_work_interrupt2 regs ffff8800c9f1bf58, eflags 217, rip 45b260
> 
>             perf-893   [003] d...  1358.053652: prepare_exit_to_usermode: prepare_exit_to_usermode1 regs ffff8800c9f1bf58, eflags 217, rip 45b260
> 
> 
> this is trace_printk output for OLD microcode 0x6000822:
> 
> DEBUG EX
>             perf-898   [005] d...    87.098816: sync_regs: sync_regs eregs ffff88012ed47f58, regs ffff8800c9c8ff58
>             perf-898   [005] d...    87.098817: do_debug: do_debug-1 regs ffff8800c9c8ff58, eflags 217, rip 45b260
>             perf-898   [005] d.h.    87.098823: do_debug: do_debug-2 eflags 10217, rip 45b260
>             perf-898   [005] d...    87.098824: prepare_exit_to_usermode: prepare_exit_to_usermode1 regs ffff8800c9c8ff58, eflags 10217, rip 45b260
>             perf-898   [005] d...    87.098825: prepare_exit_to_usermode: prepare_exit_to_usermode3 regs ffff8800c9c8ff58, eflags 10217, rip 45b260
> 
> WORK_IRQ
>  --->       perf-898   [005] d...    87.098827: smp_irq_work_interrupt: smp_irq_work_interrupt1 regs ffff8800c9c8ff58, eflags 10217, rip 45b260
>             perf-898   [005] d.h.    87.098832: perf_event_wakeup: irq_work SIGIO
>             perf-898   [005] d...    87.098833: smp_irq_work_interrupt: smp_irq_work_interrupt2 regs ffff8800c9c8ff58, eflags 10217, rip 45b260
> 
>             perf-898   [005] d...    87.098833: prepare_exit_to_usermode: prepare_exit_to_usermode1 regs ffff8800c9c8ff58, eflags 10217, rip 45b260

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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