From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] Fix possible FPU information on SVM Date: Thu, 07 Jun 2007 17:08:48 +0300 Message-ID: <46681170.2080700@qumranet.com> References: <20070607140145.GD24291@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: Joerg Roedel Return-path: In-Reply-To: <20070607140145.GD24291-5C7GfCeVMHo@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Joerg Roedel wrote: > From: Joerg Roedel > > On AMD K8 processors the fxsave/fxrstor instructions do not save and > restore the x87 error pointers FIP/FOP and FDP except the ES bit in the > status word is set. This could lead to information leakage from host to > guest and vice versa. This patch fixes this by setting the error > pointers to defined values on FPU state switch in KVM. > > The host already has full access to the guest fpu state, so there's no gain in clearing the error pointers after the guest exit. Am I right in assuming that the error data itself cannot cause any problems? The first bit (before guest entry) is needed, though I have a hard time seeing what a guest could to with the error pointers. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/