Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753377Ab3JBOHB (ORCPT ); Wed, 2 Oct 2013 10:07:01 -0400 Received: from mail-ea0-f180.google.com ([209.85.215.180]:62965 "EHLO mail-ea0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752425Ab3JBOG2 (ORCPT ); Wed, 2 Oct 2013 10:06:28 -0400 From: Paolo Bonzini To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, gleb@redhat.com Subject: [PATCH 2/3] KVM: x86: prevent setting unsupported XSAVE states Date: Wed, 2 Oct 2013 16:06:15 +0200 Message-Id: <1380722776-12358-3-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1380722776-12358-1-git-send-email-pbonzini@redhat.com> References: <1380722776-12358-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3278 Lines: 103 A guest can still attempt to save and restore XSAVE states even if they have been masked in CPUID leaf 0Dh. This usually is not visible to the guest, but is still wrong: "Any attempt to set a reserved bit (as determined by the contents of EAX and EDX after executing CPUID with EAX=0DH, ECX= 0H) in XCR0 for a given processor will result in a #GP exception". The patch also performs the same checks as __kvm_set_xcr in KVM_SET_XSAVE. This catches migration from newer to older kernel/processor before the guest starts running. Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 8 ++++++++ arch/x86/kvm/x86.c | 18 +++++++++++++++--- 3 files changed, 24 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index c76ff74..35d10d1 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -389,6 +389,7 @@ struct kvm_vcpu_arch { struct fpu guest_fpu; u64 xcr0; + u64 guest_supported_xcr0; struct kvm_pio_request pio; void *pio_data; diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a03a9fa..5a5ff94 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -46,6 +46,14 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu) apic->lapic_timer.timer_mode_mask = 1 << 17; } + best = kvm_find_cpuid_entry(vcpu, 0xD, 0); + if (!best) + vcpu->arch.guest_supported_xcr0 = 0; + else + vcpu->arch.guest_supported_xcr0 = + (best->eax | ((u64)best->edx << 32)) & + host_xcr0 & KVM_SUPPORTED_XCR0; + kvm_pmu_cpuid_update(vcpu); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 187f824..7d5c520 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -586,7 +586,7 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) return 1; if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE)) return 1; - if (xcr0 & ~host_xcr0) + if (xcr0 & ~vcpu->arch.guest_supported_xcr0) return 1; kvm_put_guest_xcr0(vcpu); vcpu->arch.xcr0 = xcr0; @@ -3003,10 +3003,19 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu, u64 xstate_bv = *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)]; - if (cpu_has_xsave) + if (cpu_has_xsave) { + /* + * Here we allow setting states that are not present in + * CPUID leaf 0xD, index 0, EDX:EAX. This is for compatibility + * with old userspace. + */ + if (xstate_bv & ~KVM_SUPPORTED_XCR0) + return -EINVAL; + if (xstate_bv & ~host_xcr0) + return -EINVAL; memcpy(&vcpu->arch.guest_fpu.state->xsave, guest_xsave->region, xstate_size); - else { + } else { if (xstate_bv & ~XSTATE_FPSSE) return -EINVAL; memcpy(&vcpu->arch.guest_fpu.state->fxsave, @@ -6940,6 +6949,9 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) vcpu->arch.ia32_tsc_adjust_msr = 0x0; vcpu->arch.pv_time_enabled = false; + + vcpu->arch.guest_supported_xcr0 = 0; + kvm_async_pf_hash_reset(vcpu); kvm_pmu_init(vcpu); -- 1.8.3.1 -- 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/