From 2af4f5fde8e45ad3595987a086c35fed7a1280ee Mon Sep 17 00:00:00 2001
From: Ram Pai <linuxram@us.ibm.com>
Date: Mon, 6 Nov 2017 00:50:49 -0800
Subject: [PATCH 16/45] powerpc: shifted-by-one hidx value
References: FATE#322447, bsc#1078248
Patch-mainline: v4.16-rc1
Git-commit: 7b84947cadf18f9a7763f281509db1f24073b4af
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>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/include/asm/book3s/64/hash-64k.h | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index a5dd4db9d286..e933928e3f4d 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -62,13 +62,21 @@ static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep)
return rpte;
}
+/*
+ * shift the hidx representation by one-modulo-0xf; i.e hidx 0 is respresented
+ * as 1, 1 as 2,... , and 0xf as 0. This convention lets us represent a
+ * invalid hidx 0xf with a 0x0 bit value. PTEs are anyway zero'd when
+ * allocated. We dont have to zero them gain; thus save on the initialization.
+ */
+#define HIDX_UNSHIFT_BY_ONE(x) ((x + 0xfUL) & 0xfUL) /* shift backward by one */
+#define HIDX_SHIFT_BY_ONE(x) ((x + 0x1UL) & 0xfUL) /* shift forward by one */
#define HIDX_BITS(x, index) (x << (index << 2))
#define BITS_TO_HIDX(x, index) ((x >> (index << 2)) & 0xfUL)
-#define INVALID_RPTE_HIDX ~(0x0UL)
+#define INVALID_RPTE_HIDX 0x0UL
static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
{
- return BITS_TO_HIDX(rpte.hidx, index);
+ return HIDX_UNSHIFT_BY_ONE(BITS_TO_HIDX(rpte.hidx, index));
}
/*
@@ -81,7 +89,7 @@ static inline unsigned long pte_set_hidx(pte_t *ptep, real_pte_t rpte,
unsigned long *hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
rpte.hidx &= ~HIDX_BITS(0xfUL, subpg_index);
- *hidxp = rpte.hidx | HIDX_BITS(hidx, subpg_index);
+ *hidxp = rpte.hidx | HIDX_BITS(HIDX_SHIFT_BY_ONE(hidx), subpg_index);
/*
* Anyone reading PTE must ensure hidx bits are read after reading the
--
2.13.6