Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752344Ab3IHJyu (ORCPT ); Sun, 8 Sep 2013 05:54:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62892 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752096Ab3IHJys (ORCPT ); Sun, 8 Sep 2013 05:54:48 -0400 Date: Sun, 8 Sep 2013 12:54:46 +0300 From: Gleb Natapov To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH] KVM: x86: prevent setting unsupported XSAVE states Message-ID: <20130908095446.GE17294@redhat.com> References: <1378383714-9723-2-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1378383714-9723-2-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: 3098 Lines: 90 On Thu, Sep 05, 2013 at 02:21:54PM +0200, Paolo Bonzini wrote: > 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. > > Cc: kvm@vger.kernel.org > Cc: Gleb Natapov > Signed-off-by: Paolo Bonzini > --- > arch/x86/kvm/cpuid.c | 2 +- > arch/x86/kvm/x86.c | 10 ++++++++-- > arch/x86/kvm/x86.h | 1 + > 3 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index a20ecb5..d7c465d 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -182,7 +182,7 @@ static bool supported_xcr0_bit(unsigned bit) > { > u64 mask = ((u64)1 << bit); > > - return mask & (XSTATE_FP | XSTATE_SSE | XSTATE_YMM) & host_xcr0; > + return mask & KVM_SUPPORTED_XCR0 & host_xcr0; > } > > #define F(x) bit(X86_FEATURE_##x) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 3625798..801a882 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -586,6 +586,8 @@ 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 & ~KVM_SUPPORTED_XCR0) > + return 1; Shouldn't we check guest's cpuid here? > if (xcr0 & ~host_xcr0) > return 1; > kvm_put_guest_xcr0(vcpu); > @@ -2980,10 +2982,14 @@ 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) { > + if (xstate_bv & ~KVM_SUPPORTED_XCR0) > + return -EINVAL; > + if (xstate_bv & ~host_xcr0) > + return -EINVAL; And here? > 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, > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index e224f7a..587fb9e 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -122,6 +122,7 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt, > gva_t addr, void *val, unsigned int bytes, > struct x86_exception *exception); > > +#define KVM_SUPPORTED_XCR0 (XSTATE_FP | XSTATE_SSE | XSTATE_YMM) > extern u64 host_xcr0; > > extern struct static_key kvm_no_apic_vcpu; > -- > 1.8.3.1 -- Gleb. -- 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/