[U-Boot] [PATCH v4 04/16] sandbox: smbios: Update to support sandbox

[Simon Glass]

Hi Alex,

On 3 June 2018 at 04:13, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 25.05.18 04:42, Simon Glass wrote:
>> Hi Alex,
>>
>> On 24 May 2018 at 06:24, Alexander Graf <agraf at suse.de> wrote:
>>>
>>>
>>> On 16.05.18 17:42, Simon Glass wrote:
>>>> At present this code casts addresses to pointers so cannot be used with
>>>> sandbox. Update it to use mapmem instead.
>>>>
>>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>
>>> I really dislike the whole fact that you have to call map_sysmem() at
>>> all. I don't quite understand the whole point of it either - it just
>>> seems to clutter the code and make it harder to follow.
>>
>> The purpose is to map U-Boot addresses (e.g. 0x1234) to actual
>> user-space addresses in sandbox (gd->arch.ram_buf + 0x1234).
>>
>> Otherwise we cannot write tests which use particular addresses, and
>> people have to worry about the host memory layout when using sandbox.
>
> Not if we write a smart enough linker script. I can try to see when I
> get around to give you an example. But basically all we need to do is
> reserve a section for guest ram at a constant virtual address.

Yes, but ideally that would be 0, or something small.

>
>>> Can't we just simply make sandbox behave like any other target instead?
>>
>> Actually that's the goal of the sandbox support. Memory is modelled as
>> a contiguous chunk starting at 0x0, regardless of what the OS actually
>> gives U-Boot in terms of addresses.
>
> Most platforms don't have RAM start at 0x0 (and making sure nobody
> assumes it does start at 0 is a good thing). The only bit we need to
> make sure is that it always starts at *the same* address on every
> invocation. But if that address is 256MB, things should still be fine.

Yes but putting a 10000000 base address on everything is a bit of a pain.

Regards,
Simon