Re: [PATCH v3 5/7] firmware: coreboot: Remap RAM with memremap() instead of ioremap()

[Stephen Boyd <swboyd@chromium.org>]

Quoting Julius Werner (2018-08-09 11:24:29)
> One thing to note is that we still want this space to be mappable by
> userspace applications via /dev/mem, so we need to make sure that
> there's no weird memory type mismatch that causes problems with that.
> Adding Aaron to see if he has any concerns here, since I think he's
> seen something like that in the past (not sure if it was related to
> what this kernel driver does).
> 
> Can you please test this on an x86 Chromebook and run the 'cbmem'
> userspace utility, make sure it doesn't fail after this?

Sure!

> 
> Also, stupid question after taking a step back and looking at this
> again: why do we keep a mapping alive for the lifetime of the driver
> at all? It used to be necessary when this driver was
> find-entry-on-demand, but nowadays it just goes through all entries
> once at probe time and immediately memcpy_fromio()s out all the
> relevant information into (struct coreboot_device)s. After that we're
> done accessing the "real" coreboot table, forever. Why not just unmap
> it again at the end of coreboot_table_init()?

Yes, we just copy everything over so it makes it simpler to just unmap
at the end of coreboot_table_init(). Then userspace is free to make a
questionable mapping into system RAM to find the table itself.

I'll make this change.