Re: [PATCH V2 10/11] powerpc/mm/radix: Make max pfn bits a variable

[Aneesh Kumar K.V]

Paul Mackerras  writes:

> On Thu, Mar 16, 2017 at 04:02:08PM +0530, Aneesh Kumar K.V wrote:
>> This makes max pysical address bits a variable so that hash and radix
>> translation mode can choose what value to use. In this patch we also switch 
>> the
>> radix translation mode to use 57 bits. This make it resilient to future 
>> changes
>> to max pfn supported by platforms.
>> 
>> This patch is split from the previous one to make the review easier.
>> 
>> Signed-off-by: Aneesh Kumar K.V 
>
> Why do we need to do this now?  It seems like this will add overhead
> every time we set a PTE for no current benefit.

I was trying to make sure that radix kernel can run on future version of
hardware where the max pfn bit is different.

-aneesh

Re: [PATCH V2 10/11] powerpc/mm/radix: Make max pfn bits a variable

[Paul Mackerras]

On Thu, Mar 16, 2017 at 04:02:08PM +0530, Aneesh Kumar K.V wrote:
> This makes max pysical address bits a variable so that hash and radix
> translation mode can choose what value to use. In this patch we also switch 
> the
> radix translation mode to use 57 bits. This make it resilient to future 
> changes
> to max pfn supported by platforms.
> 
> This patch is split from the previous one to make the review easier.
> 
> Signed-off-by: Aneesh Kumar K.V 

Why do we need to do this now?  It seems like this will add overhead
every time we set a PTE for no current benefit.

Paul.

[PATCH V2 10/11] powerpc/mm/radix: Make max pfn bits a variable

[Aneesh Kumar K.V]

This makes max pysical address bits a variable so that hash and radix
translation mode can choose what value to use. In this patch we also switch the
radix translation mode to use 57 bits. This make it resilient to future changes
to max pfn supported by platforms.

This patch is split from the previous one to make the review easier.

Signed-off-by: Aneesh Kumar K.V 
---
 arch/powerpc/include/asm/book3s/64/hash.h| 18 ++
 arch/powerpc/include/asm/book3s/64/pgtable.h | 28 +---
 arch/powerpc/include/asm/book3s/64/radix.h   |  4 
 arch/powerpc/mm/hash_utils_64.c  |  1 +
 arch/powerpc/mm/pgtable-radix.c  |  1 +
 arch/powerpc/mm/pgtable_64.c |  3 +++
 6 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h 
b/arch/powerpc/include/asm/book3s/64/hash.h
index ec2828b1db07..af3c88624d3a 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -20,6 +20,24 @@
 #define H_PAGE_F_GIX   (_RPAGE_RSV2 | _RPAGE_RSV3 | _RPAGE_RSV4)
 #define H_PAGE_F_SECOND_RPAGE_RSV1 /* HPTE is in 2ndary 
HPTEG */
 #define H_PAGE_HASHPTE _RPAGE_SW0  /* PTE has associated HPTE */
+/*
+ * Max physical address bit we will use for now.
+ *
+ * This is mostly a hardware limitation and for now Power9 has
+ * a 51 bit limit.
+ *
+ * This is different from the number of physical bit required to address
+ * the last byte of memory. That is defined by MAX_PHYSMEM_BITS.
+ * MAX_PHYSMEM_BITS is a linux limitation imposed by the maximum
+ * number of sections we can support (SECTIONS_SHIFT).
+ *
+ * This is different from Radix page table limitation and
+ * should always be less than that. The limit is done such that
+ * we can overload the bits between _RPAGE_PA_MAX and H_PAGE_PA_MAX
+ * for hash linux page table specific bits.
+ */
+#define H_PAGE_PA_MAX  51
+#define H_PTE_RPN_MASK (((1UL << H_PAGE_PA_MAX) - 1) & (PAGE_MASK))
 
 #ifdef CONFIG_PPC_64K_PAGES
 #include 
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h 
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index c470dcc815d5..eb82b60b5c89 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -40,23 +40,6 @@
 #define _RPAGE_RPN10x02000
 /* Max physicall address bit as per radix table */
 #define _RPAGE_PA_MAX  57
-/*
- * Max physical address bit we will use for now.
- *
- * This is mostly a hardware limitation and for now Power9 has
- * a 51 bit limit.
- *
- * This is different from the number of physical bit required to address
- * the last byte of memory. That is defined by MAX_PHYSMEM_BITS.
- * MAX_PHYSMEM_BITS is a linux limitation imposed by the maximum
- * number of sections we can support (SECTIONS_SHIFT).
- *
- * This is different from Radix page table limitation above and
- * should always be less than that. The limit is done such that
- * we can overload the bits between _RPAGE_PA_MAX and _PAGE_PA_MAX
- * for hash linux page table specific bits.
- */
-#define _PAGE_PA_MAX   51
 
 #define _PAGE_SOFT_DIRTY   _RPAGE_SW3 /* software: software dirty tracking 
*/
 #define _PAGE_SPECIAL  _RPAGE_SW2 /* software: special page */
@@ -70,12 +53,6 @@
  */
 #define _PAGE_NO_CACHE _PAGE_TOLERANT
 /*
- * We support _RPAGE_PA_MAX bit real address in pte. On the linux side
- * we are limited by _PAGE_PA_MAX. Clear everything above _PAGE_PA_MAX
- * every thing below PAGE_SHIFT;
- */
-#define PTE_RPN_MASK   (((1UL << _PAGE_PA_MAX) - 1) & (PAGE_MASK))
-/*
  * set of bits not changed in pmd_modify. Even though we have hash specific 
bits
  * in here, on radix we expect them to be zero.
  */
@@ -180,6 +157,11 @@
 
 #ifndef __ASSEMBLY__
 /*
+ * based on max physical address bit that we want to encode in page table
+ */
+extern unsigned long __pte_rpn_mask;
+#define PTE_RPN_MASK __pte_rpn_mask
+/*
  * page table defines
  */
 extern unsigned long __pte_index_size;
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h 
b/arch/powerpc/include/asm/book3s/64/radix.h
index ac16d1943022..142739b31174 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -24,6 +24,10 @@
 
 /* An empty PTE can still have a R or C writeback */
 #define RADIX_PTE_NONE_MASK(_PAGE_DIRTY | _PAGE_ACCESSED)
+/*
+ * Clear everything above _RPAGE_PA_MAX every thing below PAGE_SHIFT
+ */
+#define RADIX_PTE_RPN_MASK (((1UL << _RPAGE_PA_MAX) - 1) & 
(PAGE_MASK))
 
 /* Bits to set in a RPMD/RPUD/RPGD */
 #define RADIX_PMD_VAL_BITS (0x8000UL | 
RADIX_PTE_INDEX_SIZE)
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index c554768b1fa2..d990c3332057 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -986,6