From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933006AbbAIPsb (ORCPT ); Fri, 9 Jan 2015 10:48:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37377 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754136AbbAIPs3 (ORCPT ); Fri, 9 Jan 2015 10:48:29 -0500 Date: Fri, 9 Jan 2015 16:47:48 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: Feng Wu , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, gleb@kernel.org, dwmw2@infradead.org, joro@8bytes.org, alex.williamson@redhat.com, jiang.liu@linux.intel.com, eric.auger@linaro.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, kvm@vger.kernel.org Subject: Re: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI Message-ID: <20150109154748.GD9877@potion.brq.redhat.com> References: <1418397300-10870-1-git-send-email-feng.wu@intel.com> <1418397300-10870-14-git-send-email-feng.wu@intel.com> <20150109145435.GA22469@potion.brq.redhat.com> <54AFEC00.80507@redhat.com> <20150109151258.GC9877@potion.brq.redhat.com> <54AFF128.1080603@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54AFF128.1080603@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-01-09 16:18+0100, Paolo Bonzini: > On 09/01/2015 16:12, Radim Krčmář wrote: > > > The chipset doesn't support it. :( > > > > I meant that we need to recompute PI entries for lowest priority > > interrupts every time guest's TPR changes. > > > > Luckily, Linux doesn't use TPR, but other OS might be a reason to drop > > lowest priority from PI optimizations. (Or make it more complicated.) > > Doing vector hashing is a possibility as well. I would like to know > what existing chipsets do in practice, then we can mimic it. When looking at /proc/interrupts from time to time, I have only seen interrupts landing on the first CPU of the set. We could also distinguish between AMD and Intel ... AMD should deliver to the highest APIC ID. (If we still need to decide after focus processor and APR checks.) I'll try to check using a more trustworthy approach.