From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Subject: [PATCH RFC 1/6] KVM: fix guest_mode optimization in kvm_make_all_cpus_request() Date: Thu, 6 Apr 2017 22:20:51 +0200 Message-ID: <20170406202056.18379-2-rkrcmar@redhat.com> References: <20170406202056.18379-1-rkrcmar@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Christoffer Dall , Andrew Jones , Marc Zyngier , Paolo Bonzini , Christian Borntraeger , Cornelia Huck , James Hogan , Paul Mackerras To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48938 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755634AbdDFUVQ (ORCPT ); Thu, 6 Apr 2017 16:21:16 -0400 In-Reply-To: <20170406202056.18379-1-rkrcmar@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: We have kvm_arch_vcpu_should_kick() to decide whether the target cpu needs to be kicked. The previous condition was wrong, because architectures that don't use vcpu->mode would not get interrupts and also suboptimal, because it sent IPI in cases where none was necessary. The situation is even more convoluted. MIPS and POWERPC return 1 from kvm_arch_vcpu_should_kick(), but implement vcpu->mode for some reason, so now they might kick uselessly. This is not a huge problem. s390, on the other hand, never changed vcpu->mode, so it would always be OUTSIDE_GUEST_MODE before and therefore didn't send IPIs. I don't see a reason why s390 had kvm_make_all_cpus_request() that did nothing but set the bit in vcpu->request, so the new behavior seems better. Signed-off-by: Radim Krčmář --- arch/s390/kvm/kvm-s390.c | 4 +--- virt/kvm/kvm_main.c | 2 +- 2 files changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index fd6cd05bb6a7..45b6d9ca5d24 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2130,9 +2130,7 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start, int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu) { - /* kvm common code refers to this, but never calls it */ - BUG(); - return 0; + return 1; } static int kvm_arch_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f489167839c4..2389e9c41cd2 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -187,7 +187,7 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req) smp_mb__after_atomic(); if (cpus != NULL && cpu != -1 && cpu != me && - kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE) + kvm_arch_vcpu_should_kick(vcpu)) cpumask_set_cpu(cpu, cpus); } if (unlikely(cpus == NULL)) -- 2.12.0