From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754425AbeCGNyJ (ORCPT ); Wed, 7 Mar 2018 08:54:09 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33600 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751159AbeCGNyH (ORCPT ); Wed, 7 Mar 2018 08:54:07 -0500 Date: Wed, 7 Mar 2018 14:53:24 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Vitaly Kuznetsov Cc: Paolo Bonzini , linux-kernel@vger.kernel.org, x86@kernel.org, Peter Xu , kvm@vger.kernel.org Subject: Re: [PATCH] KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use Message-ID: <20180307135323.GB12290@flask> References: <20180209130133.28387-1-vkuznets@redhat.com> <87r2oyzug5.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r2oyzug5.fsf@vitty.brq.redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2018-03-05 11:29+0100, Vitaly Kuznetsov: > Vitaly Kuznetsov writes: > > > Devices which use level-triggered interrupts under Windows 2016 with > > Hyper-V role enabled don't work: Windows disables EOI broadcast in SPIV > > unconditionally. Our in-kernel IOAPIC implementation emulates an old IOAPIC > > version which has no EOI register so EOI never happens. > > > > The issue was discovered and discussed a while ago: > > https://www.spinics.net/lists/kvm/msg148098.html > > > > Radim, Paolo, > > do we have a consensus here? (I wouldn't mind re-writing commit message > in case you think we shouldn't blame Windows, I just want to have the > annoying bug fixed :-) I have applied the patch, thanks. I think the commit message is correct (this is a Windows bug): * Current SDM has a different wording that only talks about EOI-broadcast suppression capability of the CPU. * The x2APIC document mentions that "the bit is reserved to 0 if the processor doesn't support Directed EOI" and IOAPIC is not a part of the processor, so I would assume that it doesn't hold. Basically, I think that the document confuses "Directed EOI" CPU feature and "directed EOI" IOAPIC feature, which got amended in SDM.