From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755953AbcKVPNU (ORCPT ); Tue, 22 Nov 2016 10:13:20 -0500 Received: from mx5-phx2.redhat.com ([209.132.183.37]:43586 "EHLO mx5-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753170AbcKVPNS (ORCPT ); Tue, 22 Nov 2016 10:13:18 -0500 Date: Tue, 22 Nov 2016 10:12:54 -0500 (EST) From: Paolo Bonzini To: Tom Lendacky Cc: Brijesh Singh , kvm@vger.kernel.org, rkrcmar@redhat.com, joro@8bytes.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de, bp@suse.de Message-ID: <661295193.1220276.1479827574755.JavaMail.zimbra@redhat.com> In-Reply-To: References: <147916172660.16347.15695649975899246333.stgit@brijesh-build-machine> <147916175150.16347.2494044229416144843.stgit@brijesh-build-machine> <63d4112c-71c4-9d6f-60dc-c5a71c03df7a@redhat.com> Subject: Re: [PATCH v1 2/3] kvm: svm: Add kvm_fast_pio_in support MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.4.164.1, 10.5.101.130] X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - FF49 (Linux)/8.0.6_GA_5922) Thread-Topic: Add kvm_fast_pio_in support Thread-Index: OXGfnz8m7sUKYG6LwanXqVzm70eRHA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- Original Message ----- > From: "Tom Lendacky" > To: "Paolo Bonzini" , "Brijesh Singh" , kvm@vger.kernel.org > Cc: rkrcmar@redhat.com, joro@8bytes.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, > hpa@zytor.com, tglx@linutronix.de, bp@suse.de > Sent: Tuesday, November 22, 2016 3:25:52 PM > Subject: Re: [PATCH v1 2/3] kvm: svm: Add kvm_fast_pio_in support > > On 11/21/2016 8:50 AM, Paolo Bonzini wrote: > > > > > > On 14/11/2016 23:15, Brijesh Singh wrote: > >> + /* For size less than 4 we merge, else we zero extend */ > >> + val = (size < 4) ? kvm_register_read(vcpu, VCPU_REGS_RAX) : 0; > > > > Are you sure it shouldn't always zero extend the high 32-bits? So "val" > > should be declared as u32. > > > > Paolo > > It should only zero extend when dealing with a 32-bit operation. Any use > of 8 or 16 bit registers leaves the upper 56 or 48 bits as is (see > section 3.1.2.3 in http://support.amd.com/TechDocs/24592.pdf). Duh, right, see also assign_register in arch/x86/kvm/emulate.c. Paolo > Thanks, > Tom > > > > >> + ret = emulator_pio_in_emulated(&vcpu->arch.emulate_ctxt, size, port, > >> + &val, 1); > >> + if (ret) { > >> + kvm_register_write(vcpu, VCPU_REGS_RAX, val); > >> + return ret; > >> + } >