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 15:19:25 +0200 Message-ID: <55534F5D.2090106@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> <555326A4.3030907@siemens.com> <55534BC0.1070505@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: ahonig@google.com To: Paolo Bonzini , Steve Rutherford , kvm@vger.kernel.org Return-path: Received: from goliath.siemens.de ([192.35.17.28]:52535 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022AbbEMNTh (ORCPT ); Wed, 13 May 2015 09:19:37 -0400 In-Reply-To: <55534BC0.1070505@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2015-05-13 15:04, Paolo Bonzini wrote: > > > On 13/05/2015 12:25, Jan Kiszka wrote: >>>>> 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? > > Well, reserving space at the beginning of the table (and communicating > the size via KVM_ENABLE_CAP is a way to "give the kernel a hint where to > look". Perhaps not the best, but simple and supports hotplug to some > extent. But then we need at least a way to differentiate between IOAPIC and MSI routes so that the loop can actually stop when hitting the first non-IOAPIC entry. Right now, this is not possible. But even that would be a kind of ugly interface. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux