Re: [PATCH v4] xen: arm: introduce uImage probe function for Dom0

[Julien Grall <julien.grall@linaro.org>]

Hi Oleksandr,

On 27/08/14 09:45, Oleksandr Dmytryshyn wrote:
> Patch adds a possibility to boot dom0 kernel from uImage.
> This is needed to improve boot-time. Comparing to zImage,
> uImage is not packed, therefore we can save time needed
> to unpack.

This is not entirely true. uImage is a container format to encapsulate 
anything you want. For instance I'm using a zImage in it.

OOI, if you don't want compress image, why not using ELF?

In any case, I think this is a good patch, it will avoid some hackish 
command in U-boot when the kernel is provided as a uImage :).

> +
> +    if ( start == 0 )
> +        printk(XENLOG_ERR "uImage start position is not defined\n");

> +
> +    info->zimage.start = start;

I think you misunderstood my point on the previous version. As Xen may 
allocate DOM0 bank anywhere in the memory, the uImage should contain a 
position independent kernel image. Otherwise the user may see failure if 
it decides to change the amount of memory for DOM0.

In general use case, I think Xen should ignore the start field and 
decide itself where to load the kernel in memory.

This will allow the user to use the same uImage to boot on bare metal 
and as DOM0. It will be very useful for Linaro testing as the image 
(kernel + distribution) is built generically. We only provide an 
additional layer with the Xen image.

Regards,

-- 
Julien Grall