From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [RFC PATCH 3/4] KVM: x86: Add EOI exit bitmap inference Date: Wed, 13 May 2015 12:25:40 +0200 Message-ID: <555326A4.3030907@siemens.com> References: <1431481652-27268-1-git-send-email-srutherford@google.com> <1431481652-27268-3-git-send-email-srutherford@google.com> <5552EB35.2070806@siemens.com> <555305A5.8060601@redhat.com> <55530702.5000407@siemens.com> <55531843.9090304@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Cc: ahonig@google.com To: Paolo Bonzini , Steve Rutherford , kvm@vger.kernel.org Return-path: Received: from david.siemens.de ([192.35.17.14]:51969 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932204AbbEMKZt (ORCPT ); Wed, 13 May 2015 06:25:49 -0400 In-Reply-To: <55531843.9090304@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2015-05-13 11:24, Paolo Bonzini wrote: > > > On 13/05/2015 10:10, Jan Kiszka wrote: >>>>>> There can even be multiple IOAPICs (thanks to your patches overcoming >>>>>> the single in-kernel instance). >>>> >>>> With multiple IOAPICs you have more than 24 GSIs per IOAPIC. That means >> I don't think that the number of pins per IOAPIC increases. At least not >> in the devices I've seen so far. > > Sorry, that was supposed to be "more than 24 GSIs for the IOAPICs". > >>>> that the above loop is broken for multiple IOAPICs. >> The worst case remains #IOAPIC * 24 iterations - if we have means to >> stop after the IOAPIC entries, not iterating over all routes. > > Yes. Which is not too bad if VCPUs can process it in parallel. > >>>> But perhaps when enabling KVM_SPLIT_IRQCHIP we can use args[0] to pass >>>> the number of IOAPIC routes that will cause EOI exits? >> And you need to ensure that their routes can be found in the table >> directly. Given IOAPIC hotplug, that may not be the first ones there... > > Can you reserve a bunch of GSIs at the beginning of the GSI space, and > use rt->map[] to access them and build the EOI exit bitmap? Ideally, userspace could give the kernel a hint where to look. It has a copy of the routing table and manages it, no? Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux