From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: 1GB hugepages and intel_xc_cpuid_policy by default disables it. Date: Fri, 10 Jan 2014 13:41:52 -0500 Message-ID: <20140110184151.GA20232@pegasus.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1W1h2x-0000BF-Me for xen-devel@lists.xenproject.org; Fri, 10 Jan 2014 18:43:07 +0000 Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xenproject.org, ian.jackson@eu.citrix.com, stefano.stabellini@eu.citrix.com, ian.campbell@citrix.com, jun.nakajima@intel.com List-Id: xen-devel@lists.xenproject.org Hey, It occured to me that when booting Linux HVM guests, the 1GB hugepage cpuid is not exposed. One needs to manually do: cpuid= ['0x80000001:edx=xxxxx1xxxxxxxxxxxxxxxxxxxxxxxxxx'] or cpuid="host,page1gb=k" (see http://lists.xenproject.org/archives/html/xen-users/2013-09/msg00083.html for some discussion about it). The machine I am using is supporting it: (XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB and this is the only way to get hugepages working (for reference here is what I have in the guest command line: "default_hugepagesz=1G hugepagesz=1G hugepages=2 hugepagesz=2M hugepages=100" and without this cpuid I get: hugepagesz: Unsupported page size 1024 M because the 1GB flag is not exposed. I was wondering why we don't check the host cpuid and set the 1GB flag (pdpe1gb) for those cases? It seems that all the pieces are in place for this to work? Thanks!