linux-kernel - Re: [PATCH 1/2] KVM: VMX: Don't expose unrestricted

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Date:   Sun, 8 Oct 2017 15:35:48 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH 1/2] KVM: VMX: Don't expose unrestricted_guest is enabled
 if ept is disabled

If it were me, I'd apply De Morgan to that expression, but the logic looks fine.

Reviewed-by: Jim Mattson <jmattson@...gle.com>

On Sat, Oct 7, 2017 at 7:35 PM, Wanpeng Li <kernellwp@...il.com> wrote:
> From: Wanpeng Li <wanpeng.li@...mail.com>
>
> SDM mentioned:
>
>  "If either the “unrestricted guest” VM-execution control or the “mode-based
>   execute control for EPT” VM- execution control is 1, the “enable EPT”
>   VM-execution control must also be 1."
>
> However, we can still observe unrestricted_guest is Y after inserting the kvm-intel.ko
> w/ ept=N. It depends on later starts a guest in order that the function
> vmx_compute_secondary_exec_control() can be executed, then both the module parameter
> and exec control fields will be amended.
>
> This patch fixes it by amending module parameter immediately during vmcs data setup.
>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---
>  arch/x86/kvm/vmx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 244e366..3e664ca 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6737,7 +6737,7 @@ static __init int hardware_setup(void)
>         if (!cpu_has_vmx_ept_ad_bits() || !enable_ept)
>                 enable_ept_ad_bits = 0;
>
> -       if (!cpu_has_vmx_unrestricted_guest())
> +       if (!cpu_has_vmx_unrestricted_guest() || !enable_ept)
>                 enable_unrestricted_guest = 0;
>
>         if (!cpu_has_vmx_flexpriority())
> --
> 2.7.4
>