linux-kernel - Re: [PATCH v4 03/13] arm/kexec: refactor for kernel/Kconfig.kexec

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Date:   Wed, 05 Jul 2023 17:53:02 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Eric DeVolder" <eric.devolder@...cle.com>,
        "Russell King" <linux@...linux.org.uk>,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>,
        "Huacai Chen" <chenhuacai@...nel.org>,
        "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
        "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        "Helge Deller" <deller@....de>,
        "Yoshinori Sato" <ysato@...rs.sourceforge.jp>,
        "Rich Felker" <dalias@...c.org>,
        "John Paul Adrian Glaubitz" <glaubitz@...sik.fu-berlin.de>,
        "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,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-ia64@...r.kernel.org, loongarch@...ts.linux.dev,
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        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
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Cc:     "WANG Xuerui" <kernel@...0n.name>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        "Nicholas Piggin" <npiggin@...il.com>,
        "Christophe Leroy" <christophe.leroy@...roup.eu>,
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        "Palmer Dabbelt" <palmer@...belt.com>,
        "Albert Ou" <aou@...s.berkeley.edu>,
        "Heiko Carstens" <hca@...ux.ibm.com>, gor@...ux.ibm.com,
        "Alexander Gordeev" <agordeev@...ux.ibm.com>,
        borntraeger@...ux.ibm.com, "Sven Schnelle" <svens@...ux.ibm.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Kees Cook" <keescook@...omium.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Frederic Weisbecker" <frederic@...nel.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        "Ard Biesheuvel" <ardb@...nel.org>,
        "Sami Tolvanen" <samitolvanen@...gle.com>,
        "Juerg Haefliger" <juerg.haefliger@...onical.com>,
        "Russell King" <rmk+kernel@...linux.org.uk>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        "Sebastian Reichel" <sebastian.reichel@...labora.com>,
        "Mike Rapoport" <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
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        "Xin Li" <xin3.li@...el.com>, "Tejun Heo" <tj@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, tsi@...oix.net,
        "Baoquan He" <bhe@...hat.com>, hbathini@...ux.ibm.com,
        sourabhjain@...ux.ibm.com,
        "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Subject: Re: [PATCH v4 03/13] arm/kexec: refactor for kernel/Kconfig.kexec

On Wed, Jul 5, 2023, at 17:22, Eric DeVolder wrote:
> On 7/5/23 10:05, Arnd Bergmann wrote:
>> On Wed, Jul 5, 2023, at 16:19, Eric DeVolder wrote:
>> 
>> I see this is now in linux-next, and it caused a few randconfig
>> build issues, these never happened in the past:
>
> Arnd,
> Thanks for looking at this!
>
> I received randconfig errors from Andrew Morton's machinery. When 
> investigating I
> found that randconfig was able to specify CRASH_DUMP without KEXEC, and 
> that lead
> to problems. I believe this situation existed prior to this series as 
> well.

On Arm, there was definitely a bug because one could enable CRASH_DUMP
without enabling KEXEC, but that had no effect at all. I only noticed
the problem testing linux-next because it turned from silently broken
into a build failure

> Specifically CRASH_DUMP does not have a dependency on KEXEC, or select 
> (only s390
> has this hole closed).
>
> For CRASH_DUMP, this series now selects KEXEC to close this gap, which is what a
> sane config would have (ie both CRASH_DUMP and KEXEC).

Right, that is the easier way out here.

> Do you think the changes outlined below are still needed?

I think only the first one still applies on arm, you need to ensure
that ARCH_SUPPORTS_CRASH_DUMP has the same dependency as
ARCH_SUPPORTS_KEXEC, or it just depends on ARCH_SUPPORTS_KEXEC.

    Arnd