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Date: Sat, 24 Nov 2012 14:18:06 -0800
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Subject: Re: [PATCH v3 11/12] x86, boot: add fields to support load bzImage
 and ramdisk high
From: Yinghai Lu <yinghai@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        linux-kernel@vger.kernel.org, Rob Landley <rob@landley.net>,
        Matt Fleming <matt.fleming@intel.com>
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On Sat, Nov 24, 2012 at 1:38 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 11/24/2012 01:30 PM, Yinghai Lu wrote:
>>>
>>>
>>> So, given the mess we now have on our hands... any suggestions how to
>>> best
>>> solve it?  There is the option of simply declaring old kexec binaries
>>> broken; they will then not work reliably with newer kernels, if they even
>>> work reliably now -- it is hard to know for certain.
>>
>>
>> yes, if the user updates kernel to be kexeced, then would be
>> reasonable to ask them to
>> update kexec-tools.
>>
>
> Careful... consider the people who use a kexec-based solution as
> bootloaders.

yes, those may not update kexec in the flash...

then, may need to use another bit in xloadflags to tell new kernel if
need to check ext_...

Field name:     xloadflags
Type:           modify (obligatory)
Offset/size:    0x236/2
Protocol:       2.12+

  This field is a bitmask.

  Bit 0 (read): CAN_BE_LOADED_ABOVE_4G
        - If 1, kernel/boot_params/cmdline/ramdisk can be above 4g,
                set by kernel.

  Bit 1 (write): LOADED_ABOVE_4G
        - If 1, kernel/boot_params/cmdline/ramdisk is loaded above 4g,
                set by bootloader, and kernel will check ext_ramdisk_image,
                ext_ramdisk_size and ext_cmd_line_ptr.