[PATCH V3 01/30] mm: Make vm_get_page_prot arch specific.

Aneesh Kumar K.V aneesh.kumar at linux.vnet.ibm.com
Fri Feb 19 13:40:00 AEDT 2016

Paul Mackerras <paulus at ozlabs.org> 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


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.


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