On 29/10/2018 23:25, Dan Williams wrote:
I'm wondering if we're adding an explicit
in this path to determine the page mapping size if that can be a
replacement for the kvm_is_reserved_pfn() check. In other words, the
goal of fixing up PageReserved() was to preclude the need for DAX-page
special casing in KVM, but if we already need add some special casing
for page size determination, might as well bypass the
kvm_is_reserved_pfn() dependency as well.
No, please don't. The kvm_is_reserved_pfn() check is for correctness,
the page-size check is for optimization. In theory you could have a
ZONE_DEVICE area that is smaller than 2MB and thus does not use huge pages.