From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [RFC] fix VMX TSC synchronicity Date: Thu, 17 Jan 2008 19:56:49 +0100 Message-ID: <20080117185649.GA2864@one.firstfloor.org> References: <20080114160647.GA15919@dmt> <478CC448.1030901@qumranet.com> <478CC819.3040106@csgraf.de> <478CCCA9.2080300@qumranet.com> <478DC453.1000404@qumranet.com> <20080116133454.GA14481@one.firstfloor.org> <478E08E5.2030507@qumranet.com> <20080116135415.GA14664@one.firstfloor.org> <20080117184349.GA17843@dmt> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , Alexander Graf , Andi Kleen , Avi Kivity To: Marcelo Tosatti Return-path: Content-Disposition: inline In-Reply-To: <20080117184349.GA17843@dmt> 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 > And turning of the TSC bit (for 32-bit guests). Turning off the TSC bit will break 64bit Linux (it checks if the cpuid bits have minimum supported features) and you don't know in advantage if a guest is 32bit or not. Ok there is a special BIOS call that the kernel issues to tell the BIOS that it is 64bit -- in theory you could intercept that one and then disable the TSC bit, but it doesn't sound very clean. Also that call wasn't in the very first 64bit kernels. -Andi ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/