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Subject: Re: [PATCH v2] x86/speculation/l1tf: Add KConfig for setting the L1D
 cache flush mode
To:     Abhishek Bhardwaj <abhishekbh@google.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     Anthony Steinhauser <asteinhauser@google.com>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Mark Gross <mgross@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tony Luck <tony.luck@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Waiman Long <longman@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>, kvm@vger.kernel.org,
        x86@kernel.org
References: <20200702213807.2511503-1-abhishekbh@google.com>
From:   Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <2dd61d8b-223b-5a61-b739-392e79f1ce92@intel.com>
Date:   Wed, 8 Jul 2020 14:58:24 +0800
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On 7/3/2020 5:38 AM, Abhishek Bhardwaj wrote:
> This change adds a new kernel configuration that sets the l1d cache
> flush setting at compile time rather than at run time.
> 
> Signed-off-by: Abhishek Bhardwaj <abhishekbh@google.com>
> 
> ---
> 
> Changes in v2:
> - Fix typo in the help of the new KConfig.
> 
>   arch/x86/kernel/cpu/bugs.c |  8 ++++++++
>   arch/x86/kvm/Kconfig       | 17 +++++++++++++++++
>   2 files changed, 25 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 0b71970d2d3d2..1dcc875cf5547 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -1406,7 +1406,15 @@ enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH;
>   #if IS_ENABLED(CONFIG_KVM_INTEL)
>   EXPORT_SYMBOL_GPL(l1tf_mitigation);
>   #endif
> +#if (CONFIG_KVM_VMENTRY_L1D_FLUSH == 1)
> +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NEVER;
> +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 2)
> +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_COND;
> +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 3)
> +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_ALWAYS;
> +#else
>   enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
> +#endif

how about

enum vmx_l1d_flush_state l1tf_vmx_mitigation =
#if (CONFIG_KVM_VMENTRY_L1D_FLUSH == 1)
	VMENTER_L1D_FLUSH_NEVER;
#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 2)
	VMENTER_L1D_FLUSH_COND;
#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 3)
	VMENTER_L1D_FLUSH_ALWAYS;
#else
	VMENTER_L1D_FLUSH_AUTO;
#endif