From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: emulator: do not needlesly sync registers from emulator ctxt to vcpu Date: Wed, 30 Mar 2011 12:38:53 +0200 Message-ID: <4D93083D.6000806@redhat.com> References: <20110329120838.GQ7766@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: mtosatti@redhat.com, kvm@vger.kernel.org To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:17227 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754217Ab1C3Ki5 (ORCPT ); Wed, 30 Mar 2011 06:38:57 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p2UAcuvD030077 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 30 Mar 2011 06:38:57 -0400 In-Reply-To: <20110329120838.GQ7766@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/29/2011 02:08 PM, Gleb Natapov wrote: > Currently we sync registers back and forth before/after exiting > to userspace for IO, but during IO device model shouldn't need to > read/write the registers, so we can as well skip those sync points. The > only exaception is broken vmware backdor interface. The new code sync > registers content during IO only if registers are read from/written to > by userspace in the middle of the IO operation and this almost never > happens in practise. While this is a nice idea, how much does it save in practice? It does introduce more complexity. -- error compiling committee.c: too many arguments to function