linux-kernel - Re: [PATCH 3/4] x86/intel lbr: down with test_thread_flag(TIF

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Message-ID: <57178775.7020701@virtuozzo.com>
Date:	Wed, 20 Apr 2016 16:43:17 +0300
From:	Dmitry Safonov <dsafonov@...tuozzo.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Robert Richter <rric@...nel.org>, <oprofile-list@...ts.sf.net>,
	Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [PATCH 3/4] x86/intel lbr: down with test_thread_flag(TIF_IA32)

On 04/20/2016 02:21 PM, Peter Zijlstra wrote:
> On Thu, Apr 14, 2016 at 12:29:12PM -0700, Andy Lutomirski wrote:
>> On Thu, Apr 14, 2016 at 11:10 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>>> @@ -724,7 +727,7 @@ static int branch_type(unsigned long from, unsigned long to, int abort)
>>>           * on 64-bit systems running 32-bit apps
>>>           */
>>>   #ifdef CONFIG_X86_64
>>> -       is64 = kernel_ip((unsigned long)addr) || !test_thread_flag(TIF_IA32);
>>> +       is64 = kernel_ip((unsigned long)addr) || user_64bit_mode(regs);
>> Peterz, looking at this some more, would it make sense to pass
>> user_regs and interrupt_regs (or whatever we'd call it) all the way
>> through to here?
> Urgh; again, wtf wasn't I Cc'ed to these patches?

Sorry for that - that was my unintentional miss on git-send-email.

> And not sure; if we never need the user regs, calling
> perf_get_user_regs() to set all that up seems like a massive waste of
> cycles.