linux-kernel - Re: [PATCH v1 4/8] kvm:vmx Pass through host CET related MSRs to Guest.

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Date:   Wed, 2 Jan 2019 11:12:47 -0800
From:   Jim Mattson <jmattson@...gle.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>, yu-cheng.yu@...el.com,
        yi.z.zhang@...el.com, hjl.tools@...il.com,
        Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v1 4/8] kvm:vmx Pass through host CET related MSRs to Guest.

On Wed, Dec 26, 2018 at 12:13 AM Yang Weijiang <weijiang.yang@...el.com> wrote:
>
> During Guest OS execution, it accesses these MSRs to
> configure CET runtime settings.
>
> Signed-off-by: Zhang Yi Z <yi.z.zhang@...ux.intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
>  arch/x86/kvm/vmx.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 25fa6bd2fb95..fa2db6248404 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11550,6 +11550,13 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>         vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_CS, MSR_TYPE_RW);
>         vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_ESP, MSR_TYPE_RW);
>         vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_EIP, MSR_TYPE_RW);
> +
> +       vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
> +       vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
> +       vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
> +       vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);
> +       vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
> +

Shouldn't this be conditional on the guest having CET support
enumerated in CPUID?

>         vmx->msr_bitmap_mode = 0;
>
>         vmx->loaded_vmcs = &vmx->vmcs01;
> --
> 2.17.1
>