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

[Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxxxxxxxxxxx>]

On Wed, Aug 27, 2014 at 5:40 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> 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 :).
I'll fix the commit message in the next patch.

>> +
>> +    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.
I've checked it (when Xen ignores the 'start' field). It works. I'll
fix it in the next patch.

> Regards,
>
> --
> Julien Grall

-- 
Oleksandr Dmytryshyn | Product Engineering and Development
GlobalLogic
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