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Re: [Xen-devel] Re: [PATCH] SeaBIOS/Xen: Compute the low RAM memory size

To: Keir Fraser <keir@xxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH] SeaBIOS/Xen: Compute the low RAM memory size in the BDA according to the e820
From: Kevin O'Connor <kevin@xxxxxxxxxxxx>
Date: Mon, 14 Nov 2011 08:43:38 -0500
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, seabios@xxxxxxxxxxx, ian.campbell@xxxxxxxxxx, Julian Pidancet <julian.pidancet@xxxxxxxxx>
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On Mon, Nov 14, 2011 at 01:23:41PM +0000, Keir Fraser wrote:
> On 14/11/2011 08:53, "Keir Fraser" <keir.xen@xxxxxxxxx> wrote:
> 
> > On 14/11/2011 03:36, "Kevin O'Connor" <kevin@xxxxxxxxxxxx> wrote:
> > 
> >> On Xen, the PCI init code isn't used, so assuming this struct doesn't
> >> need to live in real "ram", I think it could live just about anywhere
> >> past the end of ram.  Even with pciinit.c, addresses over 0xfc00000

Oops - that should have read 0xfec00000.

> >> (with the exception of a few bytes for hpet, apic, ioapic, and bios
> >> image) could be used.
> > 
> > I suggest we stick it at FC000000, and shift hvmloader's mem_alloc()

Since Xen lays out the PCI space (and assuming it wont put a PCI
device at that address) that should be fine.

> > starting address up by one page to FC001000. The acpi build code will have
> > to manually mem_hole_populate_ram() that one page before writing to it. This
> > can then be documented in hvmloader/config.h which contains a description
> > of, and defines for, the system memory map. This is by far the easiest
> > solution to this problem; manually crafting an SSDT is a right pain in the
> > arse, whereas this is maybe a 5-line patch.
> 
> Like the attached patch (untested), which is a bit larger than anticipated,
> but actually allows code to be net deleted. :-)

-Kevin

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