From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934664AbaEFJqN (ORCPT ); Tue, 6 May 2014 05:46:13 -0400 Received: from mail-ee0-f54.google.com ([74.125.83.54]:36293 "EHLO mail-ee0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934523AbaEFJqH (ORCPT ); Tue, 6 May 2014 05:46:07 -0400 Message-ID: <5368AF5A.2090905@redhat.com> Date: Tue, 06 May 2014 11:46:02 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Bandan Das , kvm@vger.kernel.org CC: Marcelo Tosatti , Gleb Natapov , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 2/3] KVM: x86: use memory_prepare in fetch helper function References: <1399336859-7227-1-git-send-email-bsd@redhat.com> <1399336859-7227-3-git-send-email-bsd@redhat.com> In-Reply-To: <1399336859-7227-3-git-send-email-bsd@redhat.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 06/05/2014 02:40, Bandan Das ha scritto: > + ret = ctxt->ops->memory_prepare(ctxt, addr, toread, > + exception, false, > + NULL, &uaddr); > + if (ret != X86EMUL_CONTINUE) > + return ret; > + > + if (unlikely(kvm_is_error_hva(uaddr))) { > + r = X86EMUL_PROPAGATE_FAULT; > + return r; > + } What you are doing here is basically optimizing kvm_read_guest_virt_helper because you know that all reads will be single-page and you do not need the "next_segment" in kvm_read_guest. Good catch, but you can use kvm_read_guest_page instead of going through ctxt->ops->memory_prepare. :) Paolo > + ret = __copy_from_user(data, (void __user *)uaddr, toread);