From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751854AbcGMPbg (ORCPT ); Wed, 13 Jul 2016 11:31:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52010 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751771AbcGMPb3 (ORCPT ); Wed, 13 Jul 2016 11:31:29 -0400 Subject: Re: [PATCH v3 12/14] KVM: x86: add a flag to disable KVM x2apic broadcast quirk To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <20160712200930.32143-1-rkrcmar@redhat.com> <20160712200930.32143-13-rkrcmar@redhat.com> <4b30aa90-24bb-c5d0-18c0-b1fb4a62014f@redhat.com> <20160713151413.GD22438@potion> Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, "Lan, Tianyu" , Igor Mammedov , Jan Kiszka , Peter Xu , Yang Zhang From: Paolo Bonzini Message-ID: <5ae63d79-ff54-8a4f-8438-16ce5ae22ca0@redhat.com> Date: Wed, 13 Jul 2016 17:30:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <20160713151413.GD22438@potion> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 13 Jul 2016 15:30:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/07/2016 17:14, Radim Krčmář wrote: > 2016-07-13 10:38+0200, Paolo Bonzini: >> On 12/07/2016 22:09, Radim Krčmář wrote: >>> @@ -619,14 +619,17 @@ static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda) >>> /* KVM APIC implementation has two quirks >>> * - dest always begins at 0 while xAPIC MDA has offset 24, >>> * - IOxAPIC messages have to be delivered (directly) to x2APIC. >>> + * >>> + * The broadcast quirk can be disabled with KVM_CAP_X2APIC_API. >> >> --verbose version: >> >> /* KVM APIC implementation has two quirks >> - * - dest always begins at 0 while xAPIC MDA has offset 24, >> - * - IOxAPIC messages have to be delivered (directly) to x2APIC. >> + * - dest always begins at 0 while xAPIC MDA has offset 24. This is >> + * just a quirk in the API and is not problematic. >> * >> - * The broadcast quirk can be disabled with KVM_CAP_X2APIC_API. >> + * - in-kernel IOAPIC messages have to be delivered directly to >> + * x2APIC, because the kernel does not support interrupt remapping. >> + * In order to support broadcast without interrupt remapping, x2APIC >> + * rewrites the destination of non-IPI messages (and also of IPIs sent >> + * from xAPIC-mode LAPICs) from APIC_BROADCAST to X2APIC_BROADCAST. > > KVM doesn't do the operation in parentheses since 394457a928e0 ("KVM: > x86: some apic broadcast modes does not work"). > > Following patches added only !ipi case (I already regret posting them). > >> + * >> + * The broadcast quirk can be disabled with KVM_CAP_X2APIC_API. This is >> + * important when userspace wants to use x2APIC-format MSIs, because >> + * APIC_BROADCAST (0xff) is a legal route for "cluster 0, CPUs 0-7". >> */ >> >> Sounds good? > > Except that one bit. (Code alone really can't explain the what happens > here.) > Ok, will fix both bits tomorrow and repush to kvm/queue. Then test, push to kvm/next, and pass the tree to you. Thanks! Paolo