From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] ignore reads to the EOI register. Date: Thu, 27 Mar 2008 14:55:39 +0200 Message-ID: <47EB994B.7080108@qumranet.com> References: <12065794361493-git-send-email-gcosta@redhat.com> <47EB586E.3090002@qumranet.com> <87hcesjpqa.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, qemu-devel@nongnu.org, "Maciej W. Rozycki" , Glauber Costa To: Andi Kleen Return-path: In-Reply-To: <87hcesjpqa.fsf@basil.nowhere.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Andi Kleen wrote: > "Maciej W. Rozycki" writes: > >> Linux performs reads to all registers written including this one >> deliberately using an RMW cycle to avoid triggering an erratum in some >> early Pentium integrated APICs. Obviously it does not matter for most of >> the world as the workaround is build-time conditional, but you'll get it >> if you build a generic "runs everywhere" kernel. >> > > It would be quite possible to make the cycle conditional on a > cpufeatures.h quirk flag that is only set on P5. Just would need to > out of line a few functions to avoid code bloat. > Or, alternatives? xchg vs mov? -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Jerdx-0007Oc-8h for qemu-devel@nongnu.org; Thu, 27 Mar 2008 08:55:45 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Jerdu-0007H8-0S for qemu-devel@nongnu.org; Thu, 27 Mar 2008 08:55:44 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Jerdt-0007Gu-Sx for qemu-devel@nongnu.org; Thu, 27 Mar 2008 08:55:41 -0400 Received: from bzq-179-150-194.static.bezeqint.net ([212.179.150.194] helo=il.qumranet.com) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Jerdt-00048n-Ev for qemu-devel@nongnu.org; Thu, 27 Mar 2008 08:55:41 -0400 Message-ID: <47EB994B.7080108@qumranet.com> Date: Thu, 27 Mar 2008 14:55:39 +0200 From: Avi Kivity MIME-Version: 1.0 References: <12065794361493-git-send-email-gcosta@redhat.com> <47EB586E.3090002@qumranet.com> <87hcesjpqa.fsf@basil.nowhere.org> In-Reply-To: <87hcesjpqa.fsf@basil.nowhere.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH] ignore reads to the EOI register. Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andi Kleen Cc: kvm-devel@lists.sourceforge.net, qemu-devel@nongnu.org, "Maciej W. Rozycki" , Glauber Costa Andi Kleen wrote: > "Maciej W. Rozycki" writes: > >> Linux performs reads to all registers written including this one >> deliberately using an RMW cycle to avoid triggering an erratum in some >> early Pentium integrated APICs. Obviously it does not matter for most of >> the world as the workaround is build-time conditional, but you'll get it >> if you build a generic "runs everywhere" kernel. >> > > It would be quite possible to make the cycle conditional on a > cpufeatures.h quirk flag that is only set on P5. Just would need to > out of line a few functions to avoid code bloat. > Or, alternatives? xchg vs mov? -- error compiling committee.c: too many arguments to function