On Tue, 2014-07-15 at 12:56 -0700, Andy Lutomirski wrote:

On Tue, Jul 15, 2014 at 12:34 PM, Toshi Kani [off-list ref] wrote:

quoted

This patch changes reserve_memtype() to handle the new WT type.
When (!pat_enabled && new_type), it continues to set either WB
or UC- to *new_type.  When pat_enabled, it can reserve a given
non-RAM range for WT.  At this point, it may not reserve a RAM
range for WT since reserve_ram_pages_type() uses the page flags
limited to three memory types, WB, WC and UC.

FWIW, last time I looked at this, it seemed like all the fancy
reserve_ram_pages stuff was unnecessary: shouldn't the RAM type be
easy to track in the direct map page tables?

Are you referring the direct map page tables as the kernel page
directory tables (pgd/pud/..)?

I think it needs to be able to keep track of the memory type per a
physical memory range, not per a translation, in order to prevent
aliasing of the memory type.

Thanks,
-Toshi

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