linux-kernel - Re: [PATCH v7 2/8] x86/crash: Introduce new options to support cpu and memory hotplug

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Message-ID: <YmkfaSAiGIYgTlvY@zn.tnic>
Date:   Wed, 27 Apr 2022 12:48:09 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Eric DeVolder <eric.devolder@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        hpa@...or.com, nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v7 2/8] x86/crash: Introduce new options to support cpu
 and memory hotplug

On Tue, Apr 26, 2022 at 03:08:26PM -0500, Eric DeVolder wrote:
> Why is it safe to examine kexec_crash_image outside the mutex? As I
> understand it, there is still the (very rare) opportunity for a kdump
> load/unload initiated via userland and this check to collide. (Similarly, I
> believe the mutex entry is almost always assured/likely.)

Yeah, I guess. As the comment in do_kexec_load() says

	"KISS: always take the mutex."

so ignore this part of the diff and let's always grab the mutex.

Sorry for the confusion.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette