[coreboot] 0xE0000/0xF0000 segment issue

[WANG FEI]

I'm curious why your seabios payload is loading to shadow RAM (C/D/E/F000
segment), this area suppose to be used by seabios, I guess since seabios is
a legacy BIOS. My suggestion is to load your seabios to a over 1MB address.

On Thu, Mar 19, 2015 at 2:38 PM, Naresh G. Solanki <
naresh.solanki.2011 at gmail.com> wrote:

> Hi All,
>
>
> I'm trying to port coreboot with seabios payload.
> Everything goes fine till the control is transferred to payload.
>
> Since payload is loaded between memory range 0xC_0000 - 0x10_0000.
>
> The problem I was facing was that the board was going to auto reboot mode
> while executing payload..
>
> Once it reboot then I'm not able  to control the processor through XDP
> until I manually do CPU reset.
>
> It keeps on rebooting once control is transferred to payload.
>
>
> To find out the cause I did detailed memory test & found out that the
> memory range 0xA0000 - 0xBFFFF & 0xE0000 - 0xFFFFF always reads 0xFF.
>
> since payload is loaded in the same region so before jmp_payload, I tried
> to read this region through XDP & found payload code exist.
>
> so I introduced wbinvd instruction just before jmp_payload & I found that
> the  XDP started reading 0xFF in the memory range  0xE0000 - 0xFFFFF.
>
> Thus from this I conclude that before the payload was able to execute
> because of cached copy of it in CPU cache & it didn't really existed in RAM.
>
> Also to enable  memory range 0xE_0000 to 0xF_FFFF  I have followed the
> guidlines  as per table 15 of the document
>
> http://www.intel.com/content/www/us/en/intelligent-systems/queens-bay/atom-e6xx-boot-requirements-app-note.html
>
> Is that OK.
> What I can do to successfully enable the memory range  0xE_0000 to
> 0xF_FFFF for read write operation so that my payload execution goes
> undisturbed.
>
> My ultimate aim is to load Windows by Seabios as payload.
>
> Thanks
> N Solanki
>
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> --
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>
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