Re: [coreboot] 0xE0000/0xF0000 segment issue

[Naresh G. Solanki]

As per reply from seabios mailing list,
the address range 0xE0000 to 0x10_0000 should have read write access and
that can be done with help of some magic bit.

Does anyone knows about these magic bits.
The processor I'm working with is atom e6xx.

-N Solanki
 On 20 Mar 2015 19:24, "WANG FEI"  wrote:
> 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 <
> [e-mail]> 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-e...
> >
> > 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