linux-kernel - Re: [PATCH v2] x86/speculation/l1tf: Add KConfig for setting the L1D cache flush mode

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Date:   Wed, 8 Jul 2020 14:58:24 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Abhishek Bhardwaj <abhishekbh@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Anthony Steinhauser <asteinhauser@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v2] x86/speculation/l1tf: Add KConfig for setting the L1D
 cache flush mode

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@...gle.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