linux-kernel - Re: [PATCH v2 17/32] arm: define __smp

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: <20160104220938-mutt-send-email-mst@redhat.com>
Date:	Mon, 4 Jan 2016 22:12:47 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	virtualization@...ts.linux-foundation.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	David Miller <davem@...emloft.net>, linux-ia64@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-metag@...r.kernel.org, linux-mips@...ux-mips.org,
	x86@...nel.org, user-mode-linux-devel@...ts.sourceforge.net,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	xen-devel@...ts.xenproject.org, Ingo Molnar <mingo@...nel.org>,
	Tony Lindgren <tony@...mide.com>,
	Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH v2 17/32] arm: define __smp_xxx

On Mon, Jan 04, 2016 at 02:36:58PM +0100, Peter Zijlstra wrote:
> On Sun, Jan 03, 2016 at 11:12:44AM +0200, Michael S. Tsirkin wrote:
> > On Sat, Jan 02, 2016 at 11:24:38AM +0000, Russell King - ARM Linux wrote:
> 
> > > My only concern is that it gives people an additional handle onto a
> > > "new" set of barriers - just because they're prefixed with __*
> > > unfortunately doesn't stop anyone from using it (been there with
> > > other arch stuff before.)
> > > 
> > > I wonder whether we should consider making the smp memory barriers
> > > inline functions, so these __smp_xxx() variants can be undef'd
> > > afterwards, thereby preventing drivers getting their hands on these
> > > new macros?
> > 
> > That'd be tricky to do cleanly since asm-generic depends on
> > ifndef to add generic variants where needed.
> > 
> > But it would be possible to add a checkpatch test for this.
> 
> Wasn't the whole purpose of these things for 'drivers' (namely
> virtio/xen hypervisor interaction) to use these?

My take out from discussion with you was that virtualization is probably
the only valid use-case.  So at David Miller's suggestion there's a
patch later in the series that adds virt_xxxx wrappers and these are
then used by virtio xen and later maybe others.

> And I suppose most of virtio would actually be modules, so you cannot do
> what I did with preempt_enable_no_resched() either.
> 
> But yes, it would be good to limit the use of these things.

Right so the trick is checkpatch warns about use of
__smp_xxx and hopefully people are not crazy enough
to use virt_xxx variants for non-virtual drivers.

-- 
MST
--
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/