powerpc: shifted-by-one hidx value

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0xf is considered invalid hidx value. It indicates absence of a backing
HPTE. A PTE is initialized to 0xf either
a) when it is new it is newly allocated to hold 4k-backing-HPTE
	or
b) Any time it gets demoted to a 4k-backing-HPTE

This patch shifts the representation by one-modulo-0xf; i.e hidx 0 is
represented as 1, 1 as 2,... , and 0xf as 0. This convention lets us
initialize the secondary-part of the PTE to all zeroes. PTEs are anyway
zero'd when allocated. We do not have to zero them again; thus saving on
the initialization.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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Ram Pai 2017-11-06 00:50:49 -08:00 • committed by Michael Ellerman

parent bf9a95f9a6

commit 7b84947cad

1 changed files with 11 additions and 3 deletions

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arch/powerpc/include/asm/book3s/64/hash-64k.h

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