linux-kernel - Re: [GIT PULL][RESEND #2] KVM Updates for 2.6.23-rc1

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 17 Jul 2007 12:26:01 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	caglar@...dus.org.tr, Avi Kivity <avi@...ranet.com>,
	linux-kernel@...r.kernel.org, kvm-devel@...ts.sourceforge.net,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [GIT PULL][RESEND #2] KVM Updates for 2.6.23-rc1

Linus Torvalds wrote:
> 
> Actually, I think the *real* solution would be:
> 
>  - add a X86_HAS_CMPXCHG8B config option, and set it for the appropriate 
>    CPU selection (P6 and up, or whatever the rule is)
> 
>  - make KVM depend on it
> 
>  - make KVM and HIGHMEM64 _select_ another config option, namely the 
>    NEEDS_CMPXCHG8B
> 
> and then we make the cpufeatures code check the CMPXCHG bit only if the 
> NEEDS_CMPXCHG8B thing is set. That gives us the best of all worlds.
> 
> Because there is no point in checking whether the CPU supports it if the 
> kernel doesn't _need_ it. Especially since we know that some CPU's lie 
> about it due to old NT bugs.
> 

Yes.  This is probably also true for other CPU feature options, at least
in the abstract (i.e. it may not apply to any of the current options).

	-hpa
-
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/