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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 3 Jul 2020 14:40:37 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Abhishek Bhardwaj <abhishekbh@...gle.com>
Cc:     Anthony Steinhauser <asteinhauser@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Waiman Long <longman@...hat.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>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86 <x86@...nel.org>, Doug Anderson <dianders@...gle.com>
Subject: Re: [PATCH v3] x86/speculation/l1tf: Add KConfig for setting the L1D
 cache flush mode

On Thu, Jul 02, 2020 at 11:43:47PM -0700, Abhishek Bhardwaj wrote:
> We have tried to steer away from kernel command line args for a few reasons.
> 
> I am paraphrasing my colleague Doug's argument here (CC'ed him as well) -
> 
> - The command line args are getting unwieldy. Kernel command line
> parameters are not a scalable way to set kernel config. It's intended
> as a super limited way for the bootloader to pass info to the kernel
> and also as a way for end users who are not compiling the kernel
> themselves to tweak kernel behavior.

Why cannot you simply add this option to CONFIG_CMDLINE at your kernel build
scripts?
 
> - Also, we know we want this setting from the start. This is a
> definite smell that it deserves to be a compile time thing rather than
> adding extra code + whatever miniscule time at runtime to pass an
> extra arg.

This might be a compile time thing in your environment, but not
necessarily it must be the same in others. For instance, what option
should distro kernels select?

> I think this was what CONFIGS were intended for. I'm happy to add all
> this to the commit message once it's approved in spirit by the
> maintainers.
> 
> On Thu, Jul 2, 2020 at 8:18 PM Anthony Steinhauser
> <asteinhauser@...gle.com> wrote:
> >
> > Yes, this probably requires an explanation why the change is necessary
> > or useful. Without that it is difficult to give some meaningful
> > feedback.
> 
> 
> 
> -- 
> Abhishek

-- 
Sincerely yours,
Mike.