From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [RFC PATCH 3/4] KVM: x86: Add EOI exit bitmap inference Date: Wed, 13 May 2015 15:04:00 +0200 Message-ID: <55534BC0.1070505@redhat.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> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: ahonig@google.com To: Jan Kiszka , Steve Rutherford , kvm@vger.kernel.org Return-path: Received: from mail-wi0-f172.google.com ([209.85.212.172]:36850 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933650AbbEMNEG (ORCPT ); Wed, 13 May 2015 09:04:06 -0400 Received: by wizk4 with SMTP id k4so197725053wiz.1 for ; Wed, 13 May 2015 06:04:05 -0700 (PDT) In-Reply-To: <555326A4.3030907@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. Paolo