[U-Boot] [PATCH v8 12/30] sandbox: Try to start the RAM buffer at a particular address

[Simon Glass]

Hi Alex,

On 22 June 2018 at 15:29, Alexander Graf <agraf at suse.de> wrote:
>
>
>> Am 22.06.2018 um 21:28 schrieb Simon Glass <sjg at chromium.org>:
>>
>> Hi Alex,
>>
>>> On 22 June 2018 at 06:10, Alexander Graf <agraf at suse.de> wrote:
>>>> On 06/21/2018 09:45 PM, Simon Glass wrote:
>>>>
>>>> Hi Alex,
>>>>
>>>>> On 21 June 2018 at 03:58, Alexander Graf <agraf at suse.de> wrote:
>>>>>
>>>>>> On 06/21/2018 04:02 AM, Simon Glass wrote:
>>>>>>
>>>>>> Hi Alex,
>>>>>>
>>>>>>> On 20 June 2018 at 02:51, Alexander Graf <agraf at suse.de> wrote:
>>>>>>>
>>>>>>>> On 06/20/2018 12:02 AM, Simon Glass wrote:
>>>>>>>>
>>>>>>>> Hi Alex,
>>>>>>>>
>>>>>>>>> On 18 June 2018 at 08:45, Alexander Graf <agraf at suse.de> wrote:
>>>>>>>>>
>>>>>>>>>> On 06/18/2018 04:08 PM, Simon Glass wrote:
>>>>>>>>>>
>>>>>>>>>> Use a starting address of 256MB which should be available. This
>>>>>>>>>> helps
>>>>>>>>>> to
>>>>>>>>>> make sandbox RAM buffers pointers more recognisable.
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Nak, this has a non-0 chance of failing, in case something else is
>>>>>>>>> already
>>>>>>>>> mapped at that address. You don't want to have your CI blow up 1% of
>>>>>>>>> the
>>>>>>>>> time due to this.
>>>>>>>>
>>>>>>>> It's just a hint though. Everything will still work if it doesn't get
>>>>>>>> this exact address.
>>>>>>>
>>>>>>>
>>>>>>> I don't see what it buys us then.
>>>>>>
>>>>>> These are my thoughts:
>>>>>>
>>>>>> 1. We get an address before 4GB which is needed for grub (so far as I
>>>>>> can
>>>>>> tell)
>>>>>
>>>>>
>>>>> We only need that in the memory map which you want virtual (U-Boot
>>>>> address
>>>>> space) anyway. So there's no need to also have the Linux address be <4GB.
>>>>
>>>> Grub cannot work without <4GB, right? I don't mind either way, but I
>>>> think it that if we are picking an address, picking a smaller one is
>>>> better.
>>>
>>>
>>> Only if you expose host pointers as memory addresses. We don't anymore, and
>>> grub doesn't care whether a pointer is >4G.
>>
>> We have to provide grub with pointers to memory with sandbox. These
>> will be pointers into the sandbox RAM buffer. If this buffer is >=4GB
>> then grub will not work, from my testing.
>
> It works just fine for me?

OK that's strange, but perhaps I am building grub wrong. I'l ltry it
again when things land.

Regards,
Simon