Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932096Ab3INMQ7 (ORCPT ); Sat, 14 Sep 2013 08:16:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62765 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752416Ab3INMQz (ORCPT ); Sat, 14 Sep 2013 08:16:55 -0400 From: Andrew Jones To: kvm@vger.kernel.org Cc: gleb@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH] [RFC] x86: kvm: remove KVM_SOFT_MAX_VCPUS Date: Sat, 14 Sep 2013 14:16:51 +0200 Message-Id: <1379161011-28239-1-git-send-email-drjones@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2408 Lines: 59 This patch removes KVM_SOFT_MAX_VCPUS and uses num_online_cpus() for KVM_CAP_NR_VCPUS instead, as ARM does. While the API doc simply says KVM_CAP_NR_VCPUS should return the recommended maximum number of vcpus, it has been returning KVM_SOFT_MAX_VCPUS, which was defined as the maximum tested number of vcpus. As that concept could be distro-specific, this patch uses the other recommended maximum, the number of physical cpus, as we never recommend configuring a guest that has more vcpus than the host has pcpus. Of course a guest can always still be configured with up to KVM_CAP_MAX_VCPUS though anyway. I've put RFC on this patch because I'm not sure if there are any gotchas lurking with this change. The change now means hosts no longer return the same number for KVM_CAP_NR_VCPUS, and that number is likely going to generally be quite a bit less than what KVM_SOFT_MAX_VCPUS was (160). I can't think of anything other than generating more warnings[1] from qemu with guests that configure more vcpus than pcpus though. [1] Actually, until 972fc544b6034a in uq/master is merged there won't be any warnings either. Signed-off-by: Andrew Jones --- arch/x86/include/asm/kvm_host.h | 1 - arch/x86/kvm/x86.c | 2 +- 2 files changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index c76ff74a98f2e..9236c63315a9b 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -32,7 +32,6 @@ #include #define KVM_MAX_VCPUS 255 -#define KVM_SOFT_MAX_VCPUS 160 #define KVM_USER_MEM_SLOTS 125 /* memory slots that are not exposed to userspace */ #define KVM_PRIVATE_MEM_SLOTS 3 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e5ca72a5cdb6d..d9d3e2ed68ee9 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2604,7 +2604,7 @@ int kvm_dev_ioctl_check_extension(long ext) r = !kvm_x86_ops->cpu_has_accelerated_tpr(); break; case KVM_CAP_NR_VCPUS: - r = KVM_SOFT_MAX_VCPUS; + r = min(num_online_cpus(), KVM_MAX_VCPUS); break; case KVM_CAP_MAX_VCPUS: r = KVM_MAX_VCPUS; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/