Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220629150625.238286-1-vkuznets@redhat.com> <20220629150625.238286-17-vkuznets@redhat.com>
In-Reply-To: <20220629150625.238286-17-vkuznets@redhat.com>
From:   Jim Mattson <jmattson@google.com>
Date:   Wed, 29 Jun 2022 11:56:38 -0700
Message-ID: <CALMp9eS_iAijAk4pdK1tjLbRp3XH-PhR1mX4gaSXztWPXJpfkA@mail.gmail.com>
Subject: Re: [PATCH v2 16/28] KVM: VMX: Tweak the special handling of
 SECONDARY_EXEC_ENCLS_EXITING in setup_vmcs_config()
To:     Vitaly Kuznetsov <vkuznets@redhat.com>
Cc:     kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Anirudh Rayabharam <anrayabh@linux.microsoft.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Jun 29, 2022 at 8:07 AM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> SECONDARY_EXEC_ENCLS_EXITING is conditionally added to the 'optional'
> checklist in setup_vmcs_config() but there's little value in doing so.
> First, as the control is optional, we can always check for its
> presence, no harm done. Second, the only real value cpu_has_sgx() check
> gives is that on the CPUs which support SECONDARY_EXEC_ENCLS_EXITING but
> don't support SGX, the control is not getting enabled. It's highly unlikely
> such CPUs exist but it's possible that some hypervisors expose broken vCPU
> models.
>
> Preserve cpu_has_sgx() check but filter the result of adjust_vmx_controls()
> instead of the input.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 89a3bbafa5af..e32d91006b80 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2528,9 +2528,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>                         SECONDARY_EXEC_PT_CONCEAL_VMX |
>                         SECONDARY_EXEC_ENABLE_VMFUNC |
>                         SECONDARY_EXEC_BUS_LOCK_DETECTION |
> -                       SECONDARY_EXEC_NOTIFY_VM_EXITING;
> -               if (cpu_has_sgx())
> -                       opt2 |= SECONDARY_EXEC_ENCLS_EXITING;
> +                       SECONDARY_EXEC_NOTIFY_VM_EXITING |
> +                       SECONDARY_EXEC_ENCLS_EXITING;
> +
>                 if (adjust_vmx_controls(min2, opt2,
>                                         MSR_IA32_VMX_PROCBASED_CTLS2,
>                                         &_cpu_based_2nd_exec_control) < 0)
> @@ -2577,6 +2577,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
>                 vmx_cap->vpid = 0;
>         }
>
> +       if (!cpu_has_sgx())
> +               _cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_ENCLS_EXITING;

NYC, but why is there a leading underscore here?

>         if (_cpu_based_exec_control & CPU_BASED_ACTIVATE_TERTIARY_CONTROLS) {
>                 u64 opt3 = TERTIARY_EXEC_IPI_VIRT;
>
> --
> 2.35.3
>
Reviewed-by: Jim Mattson <jmattson@google.com>