From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCH 6/7, RFC] x86_64: basic changes for supporting compatibility mode guest Date: Wed, 23 Aug 2006 12:32:12 +0200 Message-ID: <44EC4ACC.76E4.0078.0@novell.com> References: <44EC38F1.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org There was one more issue I forgot to mention: We must disable execution of 'syscall' in some way for compatibility domains. The question is whether to add respective detection code early into the syscall path (which would affect performance-wise all 64-bit domains) or whether to {dis,en}able the use of the instruction in the context switch code by updating EFER as needed (which would have a performance effect only when switching between a native and a compatibility domain, but the performance effect would likely be significantly greater). I'd prefer the second option, not the least because its implementation is significantly easier. Jan