From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: early_cpu_init() and identify_cpu() Date: Fri, 13 Jul 2007 17:26:43 +0100 Message-ID: References: <4697C16D.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4697C16D.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 13/7/07 17:16, "Jan Beulich" wrote: > Is there any reason (other than having things inherited this way from Linux) > that > we cannot call identify_cpu() for the boot CPU at the end of early_cpu_init() > rather than explicitly from __start_xen()? And if not, it would seem > reasonable > to me to at once move the two CR4 twiddling pieces out of __start_xen, too. > > (I'm not asking because I want to beautify the code, but because I want the > identify to happen earlier, namely I want to fully set up the VESA console as > early as possible, but there I'd like to be able to set MTRRs, which in turn > depends on identify_cpu() having executed. Isn't it a fairly safe bet that the BIOS will have done this for us and, if not, that the penalty is a performance loss (probably using WB or UC instead of WC) rather than a correctness issue? And hence, if we bother to update the MTRRs at all, then it can at least be left until later in the boot? -- Keir