linux-kernel - Re: [patch 2/8] Implement always-locked bit ops, for memory shared with an SMP hypervisor.

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: <200608030725.13713.ak@suse.de>
Date:	Thu, 3 Aug 2006 07:25:13 +0200
From:	Andi Kleen <ak@...e.de>
To:	Christoph Lameter <clameter@....com>
Cc:	virtualization@...ts.osdl.org,
	Jeremy Fitzhardinge <jeremy@...p.org>, akpm@...l.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Ian Pratt <ian.pratt@...source.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/8] Implement always-locked bit ops, for memory shared with an SMP hypervisor.

> As far as I can tell from this conversation there are special "Xen" 
> drivers that need this not the rest of the system.

Yes, but in general when a driver that runs on multiple architectures
(including IA64 btw) needs something architecture specific we usually
add it to asm, not add ifdefs.

> > > for those special xen drivers.
> > 
> > Well there might be reasons someone else uses this in the future too.
> > It's also not exactly Linux style - normally we try to add generic
> > facilities.
> 
> What possible use could there be to someone else?

e.g. for other hypervisors or possibly for special hardware access
(e.g. I could imagine it being used for some kind of cluster interconnect)
I remember Alan was using a similar hack in his EDAC drivers because
it was the only way to clear ECC errors. 

> The "atomic" ops lock/unlock crap exists only for i386 as far as I can 
> tell. As you said most architectures either always use atomic ops or 
> never. The lock/unlock atomic ops are i386 specific material that 
> better stay contained. Its arch specific and not generic.

Well we have our share of weird hacks for IA64 too in generic code.

Just adding a single line #include for a wrapper asm-generic surely isn't
a undue burden for the other architectures, and it will save some
mess in the Xen drivers.

-Andi
-
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/