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

[Alexander Graf <agraf@suse.de>]

On 25.05.18 04:42, Simon Glass wrote:
> Hi Alex,
> 
> On 24 May 2018 at 06:24, Alexander Graf <agraf@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@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.

>> 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.


Alex