Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Message-ID: <0e0d4ea1-a246-4d6d-ad24-d2d00561a27f@default>
Date:   Mon, 26 Feb 2018 02:31:24 -0800 (PST)
From:   Liran Alon <liran.alon@oracle.com>
To:     <kernellwp@gmail.com>
Cc:     <rkrcmar@redhat.com>, <pbonzini@redhat.com>,
        <linux-kernel@vger.kernel.org>, <kvm@vger.kernel.org>
Subject: Re: [PATCH v2] KVM: X86: Allow userspace to define the microcode
 version
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


----- kernellwp@gmail.com wrote:

> From: Wanpeng Li <wanpengli@tencent.com>
>=20
> Linux (among the others) has checks to make sure that certain features
>=20
> aren't enabled on a certain family/model/stepping if the microcode
> version=20
> isn't greater than or equal to a known good version.
>=20
> By exposing the real microcode version, we're preventing buggy guests
> that
> don't check that they are running virtualized (i.e., they should trust
> the
> hypervisor) from disabling features that are effectively not buggy.
>=20
> Suggested-by: Filippo Sironi <sironi@amazon.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Kr=C4=8Dm=C3=A1=C5=99 <rkrcmar@redhat.com>
> Cc: Liran Alon <liran.alon@oracle.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> v1 -> v2:
>  * add MSR_IA32_UCODE_REV to emulated_msrs
>=20
>  arch/x86/include/asm/kvm_host.h | 1 +
>  arch/x86/kvm/x86.c              | 9 +++++++--
>  2 files changed, 8 insertions(+), 2 deletions(-)
>=20
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 938d453..6e13f2f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -507,6 +507,7 @@ struct kvm_vcpu_arch {
>  =09u64 smi_count;
>  =09bool tpr_access_reporting;
>  =09u64 ia32_xss;
> +=09u32 microcode_version;
> =20
>  =09/*
>  =09 * Paging state of the vcpu
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 1a3ed81..4ae9517 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1047,6 +1047,7 @@ static u32 emulated_msrs[] =3D {
>  =09MSR_SMI_COUNT,
>  =09MSR_PLATFORM_INFO,
>  =09MSR_MISC_FEATURES_ENABLES,
> +=09MSR_IA32_UCODE_REV,
>  };
> =20
>  static unsigned num_emulated_msrs;
> @@ -2247,7 +2248,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
> =20
>  =09switch (msr) {
>  =09case MSR_AMD64_NB_CFG:
> -=09case MSR_IA32_UCODE_REV:
>  =09case MSR_IA32_UCODE_WRITE:
>  =09case MSR_VM_HSAVE_PA:
>  =09case MSR_AMD64_PATCH_LOADER:
> @@ -2255,6 +2255,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
>  =09case MSR_AMD64_DC_CFG:
>  =09=09break;
> =20
> +=09case MSR_IA32_UCODE_REV:
> +=09=09if (msr_info->host_initiated)
> +=09=09=09vcpu->arch.microcode_version =3D data >> 32;
> +=09=09break;
>  =09case MSR_EFER:
>  =09=09return set_efer(vcpu, data);
>  =09case MSR_K7_HWCR:
> @@ -2550,7 +2554,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
>  =09=09msr_info->data =3D 0;
>  =09=09break;
>  =09case MSR_IA32_UCODE_REV:
> -=09=09msr_info->data =3D 0x100000000ULL;
> +=09=09msr_info->data =3D (u64)vcpu->arch.microcode_version << 32;
>  =09=09break;
>  =09case MSR_MTRRcap:
>  =09case 0x200 ... 0x2ff:
> @@ -8232,6 +8236,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool
> init_event)
>  =09vcpu->arch.regs_dirty =3D ~0;
> =20
>  =09vcpu->arch.ia32_xss =3D 0;
> +=09vcpu->arch.microcode_version =3D 0x1;
> =20
>  =09kvm_x86_ops->vcpu_reset(vcpu, init_event);
>  }
> --=20
> 2.7.4

Reviewed-by: Liran Alon <liran.alon@oracle.com>