Re: [PATCH v9 10/10] drivers/block/pmem: Map NVDIMM with ioremap_wt()
On Wed, May 13, 2015 at 2:05 PM, Toshi Kani <toshi.kani(a)hp.com> wrote:
The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
write back the contents of the CPU caches in case of a crash.
This patch changes to use ioremap_wt(), which provides uncached
writes but cached reads, for improving read performance.
I'm thinking that for the libnd integration we don't want the pmem
driver hard coding the cache-policy decision. This is something that
should be specified to nd_pmem_region_create(). Especially
considering that platform firmware tables (NFIT) may specify the cache
policy for the range. As Matthew Wilcox mentioned offline we also
must match the DAX-to-mmap cache policy with the policy for the driver
mapping for architectures that are not capable of multiple mappings
of the same physical address with different policies.