linux-kernel - Re: [patch] x86: allow ZONE

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: <alpine.DEB.2.00.1010131832400.794@chino.kir.corp.google.com>
Date:	Wed, 13 Oct 2010 18:48:21 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Casey Dahlin <cdahlin@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] x86: allow ZONE_DMA to be configurable

On Wed, 13 Oct 2010, H. Peter Anvin wrote:

> And the value of those additional options is what?  I'd consider adding 
> this to the sewer pit called CONFIG_EMBEDDED (with a BUG_ON, not a 
> warning... sheesh)

BUG_ON() could panic the machine which would be rather unfortunate if we 
simply tried to load a driver that the kernel no longer supports because 
it doesn't have DMA.  A WARN_ON() seems much more appropriate to identify 
what the problem was.  It's not a fatal condition.

> but only if there is any demonstrable value other 
> than a trivial amount of code (kilobytes?) in exchange for a bunch of 
> crap #ifdef.
> 

The data savings is about 1% and the text savings is about 0.1% with all 
three options disabled:

7922297	1245500	 989600	10157397	 9afd55	vmlinux.before
7914674	1232700	 989472	10136846	 9aad0e	vmlinux.after

This is the only #ifdef necessary to make CONFIG_ZONE_DMA=n compile and 
CONFIG_GENERIC_ISA_DMA=n would require two additional #ifdefs 
(CONFIG_ISA_DMA_API=n would require none).  We carry this patch 
internally, so it would be trivial to send follow-up patches that do that 
if this patch is merged.
--
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/