linux-kernel - Re: [PATCH 2/2] kvm: use cpumask_var_t for cpus_hardware

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]

Date:	Mon, 8 Dec 2008 22:20:42 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Avi Kivity <avi@...hat.com>
Cc:	"kvm-devel" <kvm@...r.kernel.org>, linux-kernel@...r.kernel.org,
	Mike Travis <travis@....com>
Subject: Re: [PATCH 2/2] kvm: use cpumask_var_t for cpus_hardware_enabled

On Monday 08 December 2008 20:16:44 Avi Kivity wrote:
> Rusty Russell wrote:
> >> This isn't on stack, so it isn't buying us anything.
> >>     
> >
> > It's the CONFIG_NR_CPUS=4096 but nr_cpu_ids=4 case which we win using
> > dynamic allocation.  Gotta love distribution kernels.
> >
> >   
> 
> What does it buy? 4096/8 = 512 bytes statically allocated?

It adds up, and 4096 seems to be only the start of the insanityH^H^Hfun.

> > Not quite.  If !CONFIG_CPUMASK_OFFSTACK, cpumask_var_t == cpumask_t[1].
> > Blame Linus :)
> >   
> 
> Hm, is there a C trick which will error out when allocating something on 
> the stack, but work when allocating statically?  I can think of 
> something to do the reverse, but that doesn't help.

We also need to prevent assignment, eg:

	*foo = *bar;

Because when we allocate them, we'll cut them to size.

Cheers,
Rusty.
--
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/