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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Wed, 27 Nov 2013 07:46:01 +0100
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Subject: Re: [Qemu-devel] [PATCH] piix: fix 32bit pci hole
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To: Laszlo Ersek <lersek@redhat.com>
Cc: qemu-devel@nongnu.org


> > +    i440fx->pci_info.w32.begin = ram_size;

> But this patch also obliterates the high bound, 0xe0000000, which can
> lead to:
> - w32.end - w32.begin <= 512M, or
> - a special case of the former, w32.end < w32.begin.

ram_size is not the total amount of memory, it is low memory only.
There is another parameter to i440fx_init (above_4g_mem_size) which
holds the amount of memory which is going to be mapped above 4G.

Maximum possible value of ram_size is 0xe0000000.
For completeness:  On q35 the maximum amount of low mem is 0xb0000000.

> w32.end is set to IO_APIC_DEFAULT_ADDRESS==0xfec00000. (Which is BTW
> fine for OVMF too.) What will happen in a 6G guest, for example?

ram_size = 0xe0000000
above_4g_mem_size = 0xa0000000

cheers,
  Gerd