Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [patch 15/14] x86/dumpstack/64: Speedup in_exception_stack()
To:     Thomas Gleixner <tglx@linutronix.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>
References: <20190331214020.836098943@linutronix.de>
 <20190331215136.039902969@linutronix.de>
 <alpine.DEB.2.21.1904021214340.1676@nanos.tec.linutronix.de>
 <20190402154329.scp7i7uqevubgwrz@treble>
 <alpine.DEB.2.21.1904021746080.1676@nanos.tec.linutronix.de>
From:   Rasmus Villemoes <linux@rasmusvillemoes.dk>
Message-ID: <4db4323f-3416-54a8-27e3-c491827a2fbd@rasmusvillemoes.dk>
Date:   Tue, 2 Apr 2019 21:02:16 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.21.1904021746080.1676@nanos.tec.linutronix.de>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 02/04/2019 17.48, Thomas Gleixner wrote:
> On Tue, 2 Apr 2019, Josh Poimboeuf wrote:
>> On Tue, Apr 02, 2019 at 12:19:46PM +0200, Thomas Gleixner wrote:
>>> +/*
>>> + * Array of exception stack page descriptors. If the stack is larger than
>>> + * PAGE_SIZE, all pages covering a particular stack will have the same
>>> + * info.
>>> + */
>>> +static const struct estack_pages estack_pages[ESTACK_PAGES] ____cacheline_aligned = {
>>> +	[CONDRANGE(DF)]		= ESTACK_PAGE(DOUBLEFAULT_IST, DF),
>>> +	[CONDRANGE(NMI)]	= ESTACK_PAGE(NMI_IST, NMI),
>>> +	[PAGERANGE(DB)]		= ESTACK_PAGE(DEBUG_IST, DB),
>>> +	[CONDRANGE(MCE)]	= ESTACK_PAGE(MCE_IST, MCE),
>>
>> It would be nice if the *_IST macro naming aligned with the struct
>> cea_exception_stacks field naming.  Then you could just do, e.g.
>> ESTACKPAGE(DF).
> 
> Yes, lemme fix that up.
> 
>> Also it's a bit unfortunate that some of the stack size knowledge is
>> hard-coded here, i.e #DB always being > 1 page and non-#DB being
>> sometimes 1 page.
> 
> The problem is that there is no way to make this macro maze conditional on
> sizeof(). But my macro foo is rusty.

Eh, but why do you need the CONDRANGE thing at all? [5 ... 5] is a
perfectly fine designator, equivalent to [5]. So you can just use
PAGERANGE in all cases, no?

Rasmus