From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v5 3/4] KVM: x86: Add EOI exit bitmap inference Date: Thu, 30 Jul 2015 08:23:43 +0200 Message-ID: <55B9C2EF.7020603@siemens.com> References: <1438039062-3168-1-git-send-email-srutherford@google.com> <1438039062-3168-3-git-send-email-srutherford@google.com> <55B8C931.5090300@redhat.com> <20150729202714.GA32444@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Steve Rutherford , Paolo Bonzini Return-path: Received: from david.siemens.de ([192.35.17.14]:37728 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750766AbbG3GXv (ORCPT ); Thu, 30 Jul 2015 02:23:51 -0400 In-Reply-To: <20150729202714.GA32444@google.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2015-07-29 22:27, Steve Rutherford wrote: > On Wed, Jul 29, 2015 at 02:38:09PM +0200, Paolo Bonzini wrote: >> >> >> On 28/07/2015 01:17, Steve Rutherford wrote: >>> diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h >>> index d8cc54b..f6ce112 100644 >>> --- a/arch/x86/kvm/ioapic.h >>> +++ b/arch/x86/kvm/ioapic.h >>> @@ -9,6 +9,7 @@ struct kvm; >>> struct kvm_vcpu; >>> >>> #define IOAPIC_NUM_PINS KVM_IOAPIC_NUM_PINS >>> +#define MAX_NR_RESERVED_IOAPIC_PINS 48 >> >> Why is this needed? > This constant is used to bound the number of IOAPIC pins that are > reservable when enabling KVM_CAP_SPLIT_IRQCHIP. IIRC, x86 doesn't > support more than 2 IOAPICs. Huh? Surely not. I've already seen boxes with at least three, and I think you can even hot-plug them today via extension cards. Not saying that QEMU supports that already, even without KVM, but we must not limit ourselves in the kernel API. So please remove such a static limit on how many IOAPICs userspace can emulate or raise it to something sufficiently large that will last long enough. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux