linux-kernel - Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

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Message-ID: <20190411080927.GA30080@zn.tnic>
Date:   Thu, 11 Apr 2019 10:09:37 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     Dave Young <dyoung@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        Baoquan He <bhe@...hat.com>, Kairui Song <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on
 kexec-ed kernel

On Wed, Apr 10, 2019 at 11:34:51PM +0000, Junichi Nomura wrote:
> But efi_get_rsdp_addr() needs to check whether the kernel was
> kexec booted to avoid accessing invalid EFI table address.
> efi_get_kexec_setup_data_addr() is the only method I know
> to check if it was kexec-booted.

Your v3 had the right approach - you first check if you can get the
address as a kexec-ed kernel. If you do, you use that one and continue
the normal path.

If you don't, you fall back to efi_get_rsdp_addr() and get it directly
from EFI.

And then carve out the functionality you need to call multiple times in
helper functions like __efi_get_rsdp_addr().

Why doesn't that work anymore?

-- 
Regards/Gruss,
    Boris.

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