Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753034AbdLMMwB (ORCPT ); Wed, 13 Dec 2017 07:52:01 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:36307 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752995AbdLMMv5 (ORCPT ); Wed, 13 Dec 2017 07:51:57 -0500 X-Google-Smtp-Source: ACJfBovE1hLOSzYpzHe3jRd5s8x2G/Znrm/up2ZBw5E0uUQtPp5qjoK9FAzCFQ8ufgbpRtuxJqhBYQ== From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: wanpeng.li@hotmail.com Subject: [PATCH] KVM: x86: avoid unnecessary XSETBV on guest entry Date: Wed, 13 Dec 2017 13:51:52 +0100 Message-Id: <1513169512-28139-1-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 756 Lines: 24 xsetbv can be expensive when running on nested virtualization, try to avoid it. Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0f82e2cbf64c..daa1918031df 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -702,7 +702,8 @@ static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu) if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) && !vcpu->guest_xcr0_loaded) { /* kvm_set_xcr() also depends on this */ - xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0); + if (vcpu->arch.xcr0 != host_xcr0) + xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0); vcpu->guest_xcr0_loaded = 1; } } -- 1.8.3.1