From mboxrd@z Thu Jan 1 00:00:00 1970 From: Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [CFT PATCH v2 2/2] KVM: x86: support XSAVES usage in the host Date: Wed, 3 Dec 2014 19:45:38 +0100 Message-ID: <20141203184537.GA27128@potion.brq.redhat.com> References: <1416847414-22253-1-git-send-email-pbonzini@redhat.com> <1416847414-22253-3-git-send-email-pbonzini@redhat.com> <802AF3F4-2631-4979-A8CC-46B406546062@gmail.com> <547F1D84.9040505@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Nadav Amit , Linux Kernel Mailing List , kvm list , Wanpeng Li , Nadav Amit , hpa@linux.intel.com, Fenghua Yu To: Paolo Bonzini Return-path: Content-Disposition: inline In-Reply-To: <547F1D84.9040505@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 2014-12-03 15:26+0100, Paolo Bonzini: >=20 >=20 > On 03/12/2014 15:23, Nadav Amit wrote: > > I think it is better just to replace the last line with: > >=20 > > *(u64 *)(dest + XSAVE_HDR_OFFSET) =3D xsave->xsave_hdr.xstate_bv Yeah, or we can use this value for xstate_bv to save some copying too, diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 19e5e8f..ba2b7bd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3137,7 +3137,7 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struc= t kvm_vcpu *vcpu, static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu) { struct xsave_struct *xsave =3D &vcpu->arch.guest_fpu.state->xsave; - u64 xstate_bv =3D vcpu->arch.guest_supported_xcr0 | XSTATE_FPSSE; + u64 xstate_bv =3D xsave->xsave_hdr.xstate_bv; u64 valid; =20 /* > Right, this matches >=20 > u64 xstate_bv =3D *(u64 *)(src + XSAVE_HDR_OFFSET); > ... > xsave->xsave_hdr.xstate_bv =3D xstate_bv; >=20 > in load_xsave. Btw, we don't care about crashers from userspace? ---8<--- KVM: x86: prevent #GP with malicious xsave XRSTORS throws #GP when XSTATE_BV isn't a subset of XCOMP_BV. Make it so. SDM: XRSTORS Exceptions #GP If a bit in the XCOMP_BV field in the XSAVE header is 0 and the corresponding bit in the XSTATE_BV field is 1. (Also in SDM: 13.11 OPERATION OF XRSTORS) Signed-off-by: Radim Kr=C4=8Dm=C3=A1=C5=99 --- arch/x86/kvm/x86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ca26681..19e5e8f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3184,8 +3184,10 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8= *src) =20 /* Set XSTATE_BV and possibly XCOMP_BV. */ xsave->xsave_hdr.xstate_bv =3D xstate_bv; - if (cpu_has_xsaves) + if (cpu_has_xsaves) { xsave->xsave_hdr.xcomp_bv =3D host_xcr0 | XSTATE_COMPACTION_ENABLED; + xsave->xsave_hdr.xstate_bv &=3D xsave->xsave_hdr.xcomp_bv; + } =20 /* * Copy each region from the non-compacted offset to the --=20 2.2.0