From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: stale TLB contents? Date: Mon, 24 Jan 2011 14:00:58 +0100 Message-ID: <4D3D780A.4030001@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org Hi, in our BS2000 guest running as HVM with EPT on x86_64 I have a problem which seems to be related to stale TLB entries. I'm pretty sure I have invalidated the TLB correctly after a change of the page tables, so I've searched for possible problems in the hypervisor. Xen is version 4.0 from SLES 11 SP1. If I have read the sources correctly, neither INVLPG nor reload of CR3 are handled by the hypervisor. And I didn't find an explicit clearing of the TLB when a vcpu is switching physical cpus. So I think the following scenario is possible: - a vcpu is running on physical cpu A creating a TLB entry - the vcpu is scheduled on physical cpu B, while physical cpu A is left idle - on physical cpu B the TLB entry is cleared by INVLPG or load CR3 - the vcpu is scheduled on physical cpu A again (no other vcpu was active there in between), CR3 is same as when vcpu left cpu A - the old TLB entry from the vcpu is still valid there! Do I miss something? Juergen -- Juergen Gross Principal Developer Operating Systems TSP ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@ts.fujitsu.com Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html