linux-kernel - Re: [PATCH] x86/boot/KASLR: skip the specified crashkernel reserved region

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Message-ID: <20190225094522.GC26145@zn.tnic>
Date:   Mon, 25 Feb 2019 10:45:22 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/boot/KASLR: skip the specified crashkernel reserved
 region

On Mon, Feb 25, 2019 at 03:59:56PM +0800, Pingfan Liu wrote:
> crashkernel=x@y option may fail to reserve the required memory region if
> KASLR puts kernel into the region. To avoid this uncertainty, making KASLR
> skip the required region.

Lemme see if I understand this correctly: supplying crashkernel=X@Y
influences where KASLR would put the randomized kernel. And it should be
the other way around, IMHO. crashkernel= will have to "work" with KASLR
to find a suitable range and if the reservation at Y fails, then we tell
the user to try the more relaxed variant crashkernel=M.

-- 
Regards/Gruss,
    Boris.

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