From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH] use per-cpu variables in cpufreq Date: Tue, 31 May 2011 08:31:20 +0100 Message-ID: References: <625BA99ED14B2D499DC4E29D8138F1505CA61C06B3@shsmsx502.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <625BA99ED14B2D499DC4E29D8138F1505CA61C06B3@shsmsx502.ccr.corp.intel.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: "Tian, Kevin" , Juergen Gross Cc: "Liu, Jinsong" , "xen-devel@lists.xensource.com" , "mark.langsdorf@amd.com" List-Id: xen-devel@lists.xenproject.org On 31/05/2011 02:51, "Tian, Kevin" wrote: >> >> Well, there is a difference between logical and physical cpu hotplug. Xen is >> capable of bringing CPUs online and offline without them actually being >> physically plugged/unplugged from the mainboard. Indeed our physical hotplug >> support is relatively new and I would suspect not much used (and it supports >> only physical insertion, not removal!). >> >> Frankly there are a number of questions around CPUs that are physically >> plugged in after boot: >> * How does per-CPU ACPI state like PM info get set up? > > A hotplug-able cpu still has an ACPI CPU object in DSDT table, which may exist > in original DSDT table, or dynamically loaded later upon hotplug event. Once > dom0 ACPI recognizes a new CPU object, it will notify Xen about discovered > pm information. Thanks. I guessed there was probably some magic for this. -- Keir >> * In a system where TSCs are otherwise all perfectly in sync, does the >> firmware help us by setting up the new CPUs' TSCs likewise? > > Here what firmware can do is similar to what Xen can do, which can't ensure > you a truly synchronized TSC on new CPU. > > Thanks > Kevin >