Re: [Xen-devel] Xen on ARM: "Failed to allocate contiguous memory for dom0" with dom0_mem greater than 256MB

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-01-24 at 10:14 +0000, Ian Campbell wrote:
> As a workaround you could try changing the load addresses of Xen and
> the kernel, dtb etc used by u-boot to pack them towards the top of
> RAM. This *should* result in the entire lower half of RAM being
> available which will make it more likely to achieve the necessary
> alignment constraints for a dom0 taking up to half of the system RAM.
> I've not actually tried this 

I have now. Using the boot script from
http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions/Allwinner with:
        # cubieboard2
        # Top of RAM:        0x80000000
        # Xen relocate addr  0x7fe00000
        setenv kernel_addr_r 0x7fa00000 # 4M
        setenv fdt_addr      0x7f800000 # 2M
        setenv xen_addr_r    0x7f600000 # 2M
allows for dom0_mem=512M.

On a cubietruck with 2GB of RAM addresses 0xbxxxxxxx instead of
0x7xxxxxxx allow for dom0_mem up to 1GB.

I have added a general note on this topic to
http://wiki.xen.org/wiki/Xen_ARM_TODO#Domain_0_memory_limitation_due_to_1:1_mapping

I'm going to update
http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions/Allwinner with 
the specifics for the A20 platforms in a moment.

Ian.


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