Re: [PATCH v10 12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt()

On Fri, 2015-05-29 at 11:19 -0700, Dan Williams wrote: > On Fri, May 29, 2015 at 8:03 AM, Toshi Kani <toshi.kani(a)hp.com&gt; wrote: > > On Fri, 2015-05-29 at 07:43 -0700, Dan Williams wrote: > >> On Fri, May 29, 2015 at 2:11 AM, Borislav Petkov <bp(a)alien8.de&gt; wrote: > >> > On Wed, May 27, 2015 at 09:19:04AM -0600, Toshi Kani wrote: > >> >> The pmem driver maps NVDIMM with ioremap_nocache() as we cannot : > >> >> - pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size); > >> >> + pmem->virt_addr = ioremap_wt(pmem->phys_addr, pmem->size); > >> >> if (!pmem->virt_addr) > >> >> goto out_release_region; > >> > > >> > Dan, Ross, what about this one? > >> > > >> > ACK to pick it up as a temporary solution? > >> > >> I see that is_new_memtype_allowed() is updated to disallow some > >> combinations, but the manual seems to imply any mixing of memory types > >> is unsupported. Which worries me even in the current code where we > >> have uncached mappings in the driver, and potentially cached DAX > >> mappings handed out to userspace. > > > > is_new_memtype_allowed() is not to allow some combinations of mixing of > > memory types. When it is allowed, the requested type of ioremap_xxx() > > is changed to match with the existing map type, so that mixing of memory > > types does not happen. > > Yes, but now if the caller was expecting one memory type and gets > another one that is something I think the driver would want to know. > At a minimum I don't think we want to get emails about pmem driver > performance problems when someone's platform is silently degrading WB > to UC for example. The pmem driver creates an ioremap map to an NVDIMM range first. So, there will be no conflict at this point, unless there is a conflicting driver claiming the same NVDIMM range.