From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423000AbbA3O4n (ORCPT ); Fri, 30 Jan 2015 09:56:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37464 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422696AbbA3O4k (ORCPT ); Fri, 30 Jan 2015 09:56:40 -0500 Date: Fri, 30 Jan 2015 15:56:32 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Nadav Amit , Gleb Natapov Subject: Re: [PATCH 7/8] KVM: x86: avoid logical_map when it is invalid Message-ID: <20150130145631.GB27414@potion.redhat.com> References: <1422568135-28402-1-git-send-email-rkrcmar@redhat.com> <1422568135-28402-8-git-send-email-rkrcmar@redhat.com> <54CB5101.4010701@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54CB5101.4010701@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-01-30 10:38+0100, Paolo Bonzini: > On 29/01/2015 22:48, Radim Krčmář wrote: > > + if (hweight8(new->mode) != 1) > > Better (more optimized): > > if (new->mode & (new->mode - 1)) True, hweight needs to have X86_FEATURE_POPCNT to be efficient ... Do you know of a difference with it? new->mode & (new->mode - 1) | hweight8(new->mode) != 1 lea -0x1(%rax),%edi | popcnt %edi,%eax test %eax,%edi | cmp $1,%eax > Please add a comment to kvm_irq_delivery_to_apic_fast to explain what > you are doing. Would naming it kvm_apic_need_slow_delivery(), or something, be enough? > > + if (hweight8(map->mode) != 1) { > > + /* Not deliverable with optimized map. */ > > + ret = false; > > + goto out; > > + } > > Put this before the computation of cid and mda. The cid and mda are all > wrong with a mixed map, and the result of the "if" before is influenced > by the wrong cid. Fixed by patch 8, but better get it right here. Will do, thanks.