From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49163) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnNSx-0000oQ-Oq for qemu-devel@nongnu.org; Fri, 23 Sep 2016 06:12:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bnNSt-0002Cw-MY for qemu-devel@nongnu.org; Fri, 23 Sep 2016 06:12:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32862) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnNSt-0002C4-GF for qemu-devel@nongnu.org; Fri, 23 Sep 2016 06:12:19 -0400 Date: Fri, 23 Sep 2016 18:12:14 +0800 From: Peter Xu Message-ID: <20160923101213.GE29144@pxdev.xzpeter.org> References: <20160922210432.18680-1-rkrcmar@redhat.com> <20160922210432.18680-6-rkrcmar@redhat.com> <20160923100207.GD29144@pxdev.xzpeter.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 5/5] intel_iommu: do not allow EIM without KVM support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Radim =?utf-8?B?S3LEjW3DocWZ?= , qemu-devel@nongnu.org, Igor Mammedov , Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" On Fri, Sep 23, 2016 at 12:03:26PM +0200, Paolo Bonzini wrote: > > > On 23/09/2016 12:02, Peter Xu wrote: > > On Fri, Sep 23, 2016 at 11:27:09AM +0200, Paolo Bonzini wrote: > >> > Since the whole IOMMU feature is new and somewhat experimental, I think > >> > it's okay to just make EIM the default for >=2.8 machine types if KVM is > >> > on (using DEFINE_PROP_ON_OFF_AUTO; auto means true if KVM is on and > >> > false otherwise, and pc-2.7 would set eim=off). It means requiring > >> > kernel 4.8 by default, but I don't think it's a big deal. > > I think the problem is, even we have KVM support for x2apic, we are > > still losing QEMU part. And guests with cluster x2apic and >8 vcpus > > will not working properly on device interrupts, which can be very > > confusing to people (it can boot, but some devices just don't work > > properly, and they won't see useful information in guest dmesg). > > Yes, that's why I suggested EIM=on by default. I am confused. :( Why not we just keep people from that wrong configuration by default, until we have x2apic in QEMU? -- peterx