From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerd Hoffmann Subject: Re: bimodal PAE and compatibility Date: Mon, 08 Jan 2007 16:24:04 +0100 Message-ID: <45A26214.8040300@suse.de> References: <20070108144932.GA1557@totally.trollied.org.uk> <45A25DC0.1040401@suse.de> <20070108151609.GD1557@totally.trollied.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070108151609.GD1557@totally.trollied.org.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: John Levon Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org John Levon wrote: > On Mon, Jan 08, 2007 at 04:05:36PM +0100, Gerd Hoffmann wrote: > >>> We currently ship a PAE 32-bit domU that we can trivially make bimodal, >>> except that if we set it to "bimodal", then older Xens will default to >>> thinking the domU is not PAE: >>> >>> 353 dsi->pae_kernel = PAEKERN_no; >>> 354 if ( dsi->__elfnote_section ) >>> 355 { >>> 356 p = xen_elfnote_string(dsi, XEN_ELFNOTE_PAE_MODE); >>> 357 if ( p != NULL && strncmp(p, "yes", 3) == 0 ) >>> 358 dsi->pae_kernel = PAEKERN_extended_cr3; >>> >>> Could we have a new note instead? >> I don't think it improves the situation, for older Xens you need two >> kernels anyway, even if the only difference is the content of the >> pae_mode elf note ... > > What do you mean? Are you saying that Xen complains about an ELF note it > doesn't understand? No. Moving the bimodal flag to another elf node doesn't fix the problem that older Xen versions don't support bimodal kernels, thus you still need a pae and a non-pae kernel. As older Xens consider bimodal kernels as non-pae one bimodal and one pae kernel works too. But you can't get that down to only one kernel unless you drop support for xen versions below 3.0.4 ... cheers, Gerd -- Gerd Hoffmann