On Wed, Feb 04, 2015 at 06:58:14PM +0000, Mark Salter wrote:

On Wed, 2015-02-04 at 17:57 +0000, Catalin Marinas wrote:

quoted

On Wed, Feb 04, 2015 at 04:08:27PM +0000, Mark Salter wrote:

quoted

acpi_os_remap() is used to map ACPI tables. These tables may be in ram
which are already included in the kernel's linear RAM mapping. So we
need ioremap_cache to avoid two mappings to the same physical page
having different caching attributes.

What's the call path to acpi_os_ioremap() on such tables already in the
linear mapping? I can see an acpi_map() function which already takes
care of the RAM mapping case but there are other cases where
acpi_os_ioremap() is called directly. For example,
acpi_os_read_memory(), can it be called on both RAM and I/O?

acpi_map() is the one I've seen.

By default, if should_use_kmap() is not patched for arm64, it translates
to page_is_ram(); acpi_map() would simply use a kmap() which returns the
current kernel linear mapping on arm64.

I'm not sure about others.

Question for the ARM ACPI guys: what happens if you implement
acpi_os_ioremap() on arm64 as just ioremap()? Do you get any WARN_ON()
(__ioremap_caller() checks whether the memory is RAM)?

-- 
Catalin