From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: KVM: x86: fix maintenance of guest/host xcr0 state Date: Mon, 15 Apr 2013 23:30:13 -0300 Message-ID: <20130416023013.GA3943@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Gleb Natapov , Paolo Bonzini , Ulrich Obergfell To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:52871 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935163Ab3DPCaT (ORCPT ); Mon, 15 Apr 2013 22:30:19 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r3G2UI0J002216 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 15 Apr 2013 22:30:18 -0400 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: ** Untested **. Emulation of xcr0 writes zero guest_xcr0_loaded variable so that subsequent VM-entry reloads CPU's xcr0 with guests xcr0 value. However, this is incorrect because guest_xcr0_loaded variable is read to decide whether to reload hosts xcr0. In case the vcpu thread is scheduled out after the guest_xcr0_loaded = 0 assignment, and scheduler decides to preload FPU: switch_to { __switch_to __math_state_restore restore_fpu_checking fpu_restore_checking if (use_xsave()) fpu_xrstor_checking xrstor64 with CPU's xcr0 == guests xcr0 Fix by properly restoring hosts xcr0 during emulation of xcr0 writes. Analyzed-by: Ulrich Obergfell Signed-off-by: Marcelo Tosatti diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 999d124..222926a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -555,6 +555,25 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw) } EXPORT_SYMBOL_GPL(kvm_lmsw); +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); + vcpu->guest_xcr0_loaded = 1; + } +} + +static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu) +{ + if (vcpu->guest_xcr0_loaded) { + if (vcpu->arch.xcr0 != host_xcr0) + xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0); + vcpu->guest_xcr0_loaded = 0; + } +} + int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) { u64 xcr0; @@ -571,8 +590,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) return 1; if (xcr0 & ~host_xcr0) return 1; + kvm_put_guest_xcr0(vcpu); vcpu->arch.xcr0 = xcr0; - vcpu->guest_xcr0_loaded = 0; return 0; } @@ -5600,25 +5619,6 @@ static void inject_pending_event(struct kvm_vcpu *vcpu) } } -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); - vcpu->guest_xcr0_loaded = 1; - } -} - -static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu) -{ - if (vcpu->guest_xcr0_loaded) { - if (vcpu->arch.xcr0 != host_xcr0) - xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0); - vcpu->guest_xcr0_loaded = 0; - } -} - static void process_nmi(struct kvm_vcpu *vcpu) { unsigned limit = 2;