linux-kernel - Re: [External] Re: [PATCH 2/4] kexec: add CONFING_KEXEC_PURGATORY_SKIP

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Date:   Mon, 25 Jul 2022 21:32:59 +0800
From:   黄杰 <huangjie.albert@...edance.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Michael Roth <michael.roth@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Joerg Roedel <jroedel@...e.de>,
        Mark Rutland <mark.rutland@....com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        linux-kbuild@...r.kernel.org
Subject: Re: [External] Re: [PATCH 2/4] kexec: add CONFING_KEXEC_PURGATORY_SKIP_SIG

maybe a boot parameter ?

Jason A. Donenfeld <Jason@...c4.com> 于2022年7月25日周一 20:15写道：
>
> Hi Albert,
>
> On Mon, Jul 25, 2022 at 04:38:54PM +0800, Albert Huang wrote:
> > +config KEXEC_PURGATORY_SKIP_SIG
> > +     bool "skip kexec purgatory signature verification"
> > +     depends on ARCH_HAS_KEXEC_PURGATORY
> > +     help
> > +       this options makes the kexec purgatory do  not signature verification
> > +       which would get hundreds of milliseconds saved during kexec boot. If we can
> > +       confirm that the data of each segment loaded by kexec will not change we may
> > +       enable this option
> > +
>
> Some grammar nits here, but actually, wouldn't it be better to make this
> depend on some other signature things instead? Like if the parent kernel
> actually did a big signature computation, then maybe the purgatory step
> is needed, but if it didn't bother, then maybe you can skip it. This
> way, you don't need a compile-time option that might change some aspect
> of signature verification people might otherwise be relying on.
>
> Jason