From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [GIT PULL][RESEND #2] KVM Updates for 2.6.23-rc1 Date: Tue, 17 Jul 2007 12:26:01 -0700 Message-ID: <469D17C9.9010509@zytor.com> References: <11846910642166-git-send-email-avi@qumranet.com> <200707172139.09131.caglar@pardus.org.tr> <469D1317.1050202@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Andi Kleen , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Linus Torvalds Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org 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 ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/