Re: [Xen-devel] XEN[ARM] Master not working on Allwinner A20

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Sun, 5 Jan 2014, karim.allah.ahmed@xxxxxxxxx wrote:
> Hi Peter,
> 
> If you still can't boot with any memory bigger than 128M, as a fast 
> workaround you can apply this patch.
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index faff88e..849df3f 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -22,7 +22,7 @@
> Âstatic unsigned int __initdata opt_dom0_max_vcpus;
> Âinteger_param("dom0_max_vcpus", opt_dom0_max_vcpus);
> Â
> -static int dom0_11_mapping = 1;
> +static int dom0_11_mapping = 0;
> Â
> Â#define DOM0_MEM_DEFAULT 0x8000000 /* 128 MiB */
> Âstatic u64 __initdata dom0_mem = DOM0_MEM_DEFAULT;
> 
> 
> It's failing because none of the zones has a contiguous memory block with an 
> order bigger than 15 ( 128M ). I think this is due
> to the alignment of the phys_start with buddy system in cubieboard, I'll look 
> further and let you know if there's a cleaner
> approach to fix that.
> 
> It used to work before because the 11_mapping wasn't forced to "true" for all 
> platforms and there was a quirk exposed by the
> platform that used to express that. I think Julien removed that quirk and 
> defaulted to 11_mapping in commit
> "71952bfcbe9187765cf4010b1479af86def4fb1f"

Unfortunately dom0_11_mapping is needed if at least one device driver
for the Allwinner uses DMA.
For example, if you disable dom0_11_mapping, can you still access the
network? On the other hand if all device drivers do not use DMA we can
set dom0_11_mapping to false for this platform.

In any case I think that we could benefit from having dom0_11_mapping
user configurable from the command line.

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