Re: [Qemu-devel] [Xen-devel] [BUG 1747]Guest could't find bootable device with memory more than 3600M

["Jan Beulich" <JBeulich@suse.com>]

>>> On 13.06.13 at 16:50, Stefano Stabellini <stefano.stabellini@eu.citrix.com> wrote:
> The algorithm is going to work like this in details:
> 
> - the pci hole size is set to 0xfc000000-0xe0000000 = 448MB
> - we calculate the total mmio size, if it's bigger than the pci hole we
> raise a 64 bit relocation flag
> - if the 64 bit relocation is enabled, we relocate above 4G the first
> device that is 64-bit capable and has an MMIO size greater or equal to
> 512MB
> - if the pci hole size is now big enough for the remaining devices we
> stop the above 4G relocation, otherwise keep relocating devices that are
> 64 bit capable and have an MMIO size greater or equal to 512MB
> - if one or more devices don't fit we print an error and continue (it's
> not a critical failure, one device won't be used)

Devices with 512Mb BARs won't fit in a 448Mb hole in any case,
so there's no point in trying. Any such BARs need to be relocated.
Then for 256Mb BARs, you could see whether it's just one and fits.
Else relocate it, and all others (except for perhaps one). Then
halve the size again and start over, etc.

Jan