linux-kernel - Re: [PATCH v3] x86/speculation/l1tf: Add KConfig for setting the L1D cache flush mode

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Date:   Wed, 8 Jul 2020 12:32:27 -0700
From:   Abhishek Bhardwaj <abhishekbh@...gle.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Doug Anderson <dianders@...gle.com>,
        Anthony Steinhauser <asteinhauser@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        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>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86 <x86@...nel.org>
Subject: Re: [PATCH v3] x86/speculation/l1tf: Add KConfig for setting the L1D
 cache flush mode

On Mon, Jul 6, 2020 at 8:14 AM Waiman Long <longman@...hat.com> wrote:
>
> On 7/5/20 5:51 PM, Abhishek Bhardwaj wrote:
>
> That is why I said a comment will have to be added to highlight this
> dependency. For instance,
>
> +/*
> + * Three of the enums are explicitly assigned as the KVM_VMENTRY_L1D_FLUSH
> + * config entry in arch/x86/kvm/Kconfig depends on these values.
> + */
>   enum vmx_l1d_flush_state {
>          VMENTER_L1D_FLUSH_AUTO,
> -       VMENTER_L1D_FLUSH_NEVER,
> -       VMENTER_L1D_FLUSH_COND,
> -       VMENTER_L1D_FLUSH_ALWAYS,
> +       VMENTER_L1D_FLUSH_NEVER = 1,
> +       VMENTER_L1D_FLUSH_COND = 2,
> +       VMENTER_L1D_FLUSH_ALWAYS = 3,
>          VMENTER_L1D_FLUSH_EPT_DISABLED,
>          VMENTER_L1D_FLUSH_NOT_REQUIRED,
>   };
>
> Of course, this is just a suggestion.
>
> I'd rather avoid this dependency. However, if people are okay with the
> CONFIG option then I am happy to oblige with whatever people agree on.
> Can a maintainer chime in ? Waiman if you're the final authority on
> this, will you accept the patch if I incorporated your suggestion ?
>
> It is fine if you think this is not what you want.
>
> BTW, I am not a maintainer. However, no maintainer will give pre-approval. At least, you have to give the reason why this patch is needed in the patch itself. Before that happens, I don't see how it will get merged upstream.

I just updated the patch with the reasoning in the commit message -
https://lkml.org/lkml/2020/7/8/1325


>
> Cheers,
> Longman



-- 
Abhishek