Subject: Re: [RFC PATCH 0/9] powerpc/mm: Restructure Linux PTE on Book3S/64 to radix format

From: Michael Ellerman <[email-masked]>
Date: Mon, 22 Feb 2016 11:30:47 +1100

On Sat, 2016-02-20 at 20:10 +0530, Aneesh Kumar K.V wrote:
> Paul Mackerras <[email-masked]> writes:
> 
> > This patch series modifies the Linux PTE format used on 64-bit Book3S
> > processors (i.e. POWER server processors) to make the bits line up
> > with the PTE format used in the radix trees defined in PowerISA v3.0.
> > This will reduce the amount of further change required to make a
> > kernel that can run with either a radix MMU or a hashed page table
> > (HPT) MMU.
> > 
> > This also changes the upper levels of the tree to use real addresses
> > rather than kernel virtual addresses - that is, we no longer have the
> > 0xc000... at the top of each PGD/PUD/PMD entry.  I made this change
> > for all 64-bit machines, both embedded and server.
> > 
> > The patch series is against v4.5-rc4 plus Aneesh's "powerpc/mm/hash:
> > Clear the invalid slot information correctly" patch.
> > 
> > I have compiled this for all the defconfigs in the tree, without
> > error.  I have tested this, with the fixes branch of the powerpc tree
> > merged in, both running bare-metal on a POWER8 and in a KVM guest on
> > that POWER8 system.  In the guest I tested both 4k and 64k configs,
> > with THP enabled; in the host I tested with 64k page size and THP
> > enabled.  All these tests ran fine, including running a KVM guest on
> > the bare-metal system.  So far I have done kernel compiles in a loop
> > as the test, but I plan to run LTP and possibly some other tests.
> > 
> > Comments welcome.
> 
> I was expecting some complex changes in asm and other part of the code. That
> is one of the reason I was holding of a series like this till I get the
> radix merged.

Yeah, but you actually rewrote most/all of that code in C as part of your
earlier refactoring :)

> Now how do we want to go with this series ?. If we are taking this
> series before the books3 hash linux abstraction series, I will have to
> redo that series now on top of this.

I'd prefer to merge this first.

I know you'll have to redo your series, but hopefully some of your series can
just go away, because we don't need to abstract the PTE bits anymore.

cheers