linux-kernel - Re: [PATCH v2] x86/boot: Use EFI setup data if provided

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Message-ID: <20190325120149.GI12016@zn.tnic>
Date:   Mon, 25 Mar 2019 13:01:49 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     Dave Young <dyoung@...hat.com>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "kasong@...hat.com" <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 v2] x86/boot: Use EFI setup data if provided

On Mon, Mar 25, 2019 at 10:36:33AM +0000, Junichi Nomura wrote:
> AFAIU, early parsing is new code in v5.1-rc1 to support kexec on systems
> with hotpluggable memory with KASLR enabled. For systems that requires the
> new feature, it may be ok to say "you need to use another kexec interface"
> and/or "you need new kexec-tools".

No, this exactly should *not* happen. kexec is already full of duct tape
- don't need any more of that.

So I suggested that efi_get_rsdp_addr() should exit early on in the
kexeced kernel but making this all play nice with the kexec-ed kernel,
as Dave suggests, is better.

Now, my next question is: why does the RDSP address need to come from
kexec(1) (by way of efi_setup_data) and why can't the kexec'ed kernel
figure it out itself by parsing the EFI tables in a similar way to
efi_get_rsdp_addr ?

-- 
Regards/Gruss,
    Boris.

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