linux-kernel - Re: [PATCH v2 1/3] x86, boot: add mmio serial during compressed boot

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Date:	Sat, 13 Jul 2013 14:56:54 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Kees Cook <keescook@...omium.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Landley <rob@...dley.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-doc@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 1/3] x86, boot: add mmio serial during compressed boot

On Sat, Jul 13, 2013 at 7:53 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 07/12/2013 11:47 PM, Yinghai Lu wrote:
>>
>> for 32 bit, that is ok.
>> for 64 bit via 32bit bootloader, arch/x86/boot/compressed/head_64.S
>> will set page table for first 4G still ok.
>> for 64 bit via 64bit loader, like kexec via bzImage64, First Kernel/Kexec only
>> set ident mapping for usable range, so mmio just under 64 is not mapped.
>>
>> Looks like we need to update boot.txt to add requirement for 64bit bootloader
>> that 0-4G need to be all ident mapping?
>>
>
> I think that is an unrealistic requirement, especially if this is the
> sole user.

That will cause regression for:
64bit system with kexec/kdump bzImage64.
if second kernel carry "console=uart,mmio,0xABCD0000"

or we can extend kexec-tools to make it scan second kernel command line string
and one entry into image->segment[]

Yinghai
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