Paul Mackerras <paulus@xxxxxxxxxx> writes: > On Thu, Feb 18, 2016 at 10:20:25PM +0530, Aneesh Kumar K.V wrote: >> With next generation power processor, we are having a new mmu model >> [1] that require us to maintain a different linux page table format. >> >> Inorder to support both current and future ppc64 systems with a single >> kernel we need to make sure kernel can select between different page >> table format at runtime. With the new MMU (radix MMU) added, we will >> have to dynamically switch between different protection map. Hence >> override vm_get_page_prot instead of using arch_vm_get_page_prot. We >> also drop arch_vm_get_page_prot since only powerpc used it. > > This seems like unnecessary churn to me. Let's just make hash use the > same values as radix for things like _PAGE_RW, _PAGE_EXEC etc., and > then we don't need any of this. > I was hoping to do that after this series. Something similar to https://github.com/kvaneesh/linux/commit/0c2ac1328b678a6e187d1f2644a007204c59a047 " powerpc/mm: Add helper for page flag access in ioremap_at Instead of using variables we use static inline which get patched during boot to either hash or radix version. " That gives us a base to revert patches if we find issues with hash and still have a working radix base. So idea is to introduce radix with minimal changes to hash and then consolidate hash and radix as much as we can by updating hash linux format. -aneesh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>