linux-kernel - Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

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Message-ID: <965f770a-b103-72fb-eaef-cb337ebe8290@ce.jp.nec.com>
Date:   Tue, 23 Apr 2019 06:20:09 +0000
From:   Junichi Nomura <j-nomura@...jp.nec.com>
To:     Kairui Song <kasong@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Chao Fan" <fanc.fnst@...fujitsu.com>, Baoquan He <bhe@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

On 4/22/19 6:28 PM, Kairui Song wrote:
> The reason is the systab region is not mapped by the identity mapping
> provided by kexec. Currently kexec only create identity mapping for
> mem regions, wihch won't cover the systab. So second kernel will be
> accessing a not mapped memory region and cause fault.
> But as kexec tend to pad the map region up to PUD size, the
> systab could be included in the map by accident, so it worked on
> some machines, but that will be broken easily and unstable.

Is the mapping of ACPI tables just by luck, too?

-- 
Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.