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From:   =?UTF-8?B?6buE5p2w?= <huangjie.albert@bytedance.com>
Date:   Mon, 25 Jul 2022 21:32:59 +0800
Message-ID: <CABKxMyOcePkvAvMyrG2r08yRuxx=gK2SnMBFbKzKW6hBAdmRFw@mail.gmail.com>
Subject: Re: [External] Re: [PATCH 2/4] kexec: add CONFING_KEXEC_PURGATORY_SKIP_SIG
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Nick Desaulniers <ndesaulniers@google.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Michael Roth <michael.roth@amd.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <seanjc@google.com>,
        Joerg Roedel <jroedel@suse.de>,
        Mark Rutland <mark.rutland@arm.com>,
        Kees Cook <keescook@chromium.org>,
        linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
        linux-kbuild@vger.kernel.org
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maybe a boot parameter ?

Jason A. Donenfeld <Jason@zx2c4.com> =E4=BA=8E2022=E5=B9=B47=E6=9C=8825=E6=
=97=A5=E5=91=A8=E4=B8=80 20:15=E5=86=99=E9=81=93=EF=BC=9A
>
> 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 verifi=
cation
> > +       which would get hundreds of milliseconds saved during kexec boo=
t. 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