On Fri, May 29, 2015 at 11:32 AM, Toshi Kani <toshi.kani(a)hp.com> wrote:
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> 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>
> >> > 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->virt_addr = ioremap_wt(pmem->phys_addr,
> >> >> 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.
Hmm, I thought it would be WB due to this comment in is_new_memtype_allowed()
* PAT type is always WB for untracked ranges, so no need to check.