Re: [patch 0/6] Strong Access Ordering page attributes for POWER7

On Fri, 2008-07-04 at 09:39 +1000, Benjamin Herrenschmidt wrote:

On Wed, 2008-06-18 at 17:32 -0500, shaggy@linux.vnet.ibm.com wrote:

quoted

Andrew,

The first patch in this series hits architecture independent code, but the
rest is contained in the powerpc subtree.  Could you pick up the first
patch into -mm?  I can send the rest of them through the powerpc git tree.
The first patch and the rest of the set are independent and can be merged
in either order.

 ../..

I was wondering... how do we inform userspace that this is available ?
Same question with adding the endian bit on 4xx which I plan to do using
your infrastructure...

I hadn't really given it much thought.  Is there a simple way to
determine if the cpu is power 7 or newer?

It's not elegant, but a program could call mmap() with PROT_SAO set and
check for errno == EINVAL.  Then call again without PROT_SAO, if it
needs to.

We haven't defined a user-visible feature bit (and besides, we're really
getting short on these...). This is becoming a bit of concern btw (the
running out of bits). Maybe we should start defining an AT_HWCAP2 for
powerpc and get libc updated to pick it up ?

Joel,
Any thoughts?

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center