* [PATCH 0/3] Make PMD_ORDER generically available
@ 2021-07-15 13:46 Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER Matthew Wilcox (Oracle)
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Matthew Wilcox (Oracle) @ 2021-07-15 13:46 UTC (permalink / raw)
To: linux-arch, linux-parisc, linux-mips, linux-arm-kernel
Cc: Matthew Wilcox (Oracle), linux-kernel
These three architectures each define PMD_ORDER to mean "the order of
an allocation for a PMD table", but logically PMD_ORDER should be the
order of a PMD allocation, ie (PMD_SHIFT - PAGE_SHIFT) as DAX defines it.
Could each architecture maintainer please apply the appropriate patch
to their respective trees?
Matthew Wilcox (Oracle) (3):
arm: Rename PMD_ORDER to PMD_TABLE_ORDER
mips: Rename PMD_ORDER to PMD_TABLE_ORDER
parisc: Rename PMD_ORDER to PMD_TABLE_ORDER
arch/arm/kernel/head.S | 34 +++++++++++++++---------------
arch/mips/include/asm/pgalloc.h | 2 +-
arch/mips/include/asm/pgtable-32.h | 2 +-
arch/mips/include/asm/pgtable-64.h | 18 ++++++++--------
arch/mips/kernel/asm-offsets.c | 2 +-
arch/parisc/include/asm/pgalloc.h | 6 +++---
arch/parisc/include/asm/pgtable.h | 4 ++--
arch/parisc/mm/init.c | 4 ++--
8 files changed, 36 insertions(+), 36 deletions(-)
--
2.30.2
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 13:46 [PATCH 0/3] Make PMD_ORDER generically available Matthew Wilcox (Oracle)
@ 2021-07-15 13:46 ` Matthew Wilcox (Oracle)
2021-07-15 16:47 ` Russell King (Oracle)
2021-07-15 13:46 ` [PATCH 2/3] mips: " Matthew Wilcox (Oracle)
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: Matthew Wilcox (Oracle) @ 2021-07-15 13:46 UTC (permalink / raw)
To: linux-arch, linux-parisc, linux-mips, linux-arm-kernel
Cc: Matthew Wilcox (Oracle), linux-kernel
This is the order of the page table allocation, not the order of a PMD.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
arch/arm/kernel/head.S | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 9eb0b4dbcc12..6da39a1d70ba 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -38,10 +38,10 @@
#ifdef CONFIG_ARM_LPAE
/* LPAE requires an additional page for the PGD */
#define PG_DIR_SIZE 0x5000
-#define PMD_ORDER 3
+#define PMD_TABLE_ORDER 3
#else
#define PG_DIR_SIZE 0x4000
-#define PMD_ORDER 2
+#define PMD_TABLE_ORDER 2
#endif
.globl swapper_pg_dir
@@ -237,7 +237,7 @@ __create_page_tables:
mov r6, r6, lsr #SECTION_SHIFT
1: orr r3, r7, r5, lsl #SECTION_SHIFT @ flags + kernel base
- str r3, [r4, r5, lsl #PMD_ORDER] @ identity mapping
+ str r3, [r4, r5, lsl #PMD_TABLE_ORDER] @ identity mapping
cmp r5, r6
addlo r5, r5, #1 @ next section
blo 1b
@@ -247,13 +247,13 @@ __create_page_tables:
* set two variables to indicate the physical start and end of the
* kernel.
*/
- add r0, r4, #KERNEL_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
+ add r0, r4, #KERNEL_OFFSET >> (SECTION_SHIFT - PMD_TABLE_ORDER)
ldr r6, =(_end - 1)
adr_l r5, kernel_sec_start @ _pa(kernel_sec_start)
str r8, [r5] @ Save physical start of kernel
orr r3, r8, r7 @ Add the MMU flags
- add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
-1: str r3, [r0], #1 << PMD_ORDER
+ add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_TABLE_ORDER)
+1: str r3, [r0], #1 << PMD_TABLE_ORDER
add r3, r3, #1 << SECTION_SHIFT
cmp r0, r6
bls 1b
@@ -269,14 +269,14 @@ __create_page_tables:
mov r3, pc
mov r3, r3, lsr #SECTION_SHIFT
orr r3, r7, r3, lsl #SECTION_SHIFT
- add r0, r4, #(XIP_START & 0xff000000) >> (SECTION_SHIFT - PMD_ORDER)
- str r3, [r0, #((XIP_START & 0x00f00000) >> SECTION_SHIFT) << PMD_ORDER]!
+ add r0, r4, #(XIP_START & 0xff000000) >> (SECTION_SHIFT - PMD_TABLE_ORDER)
+ str r3, [r0, #((XIP_START & 0x00f00000) >> SECTION_SHIFT) << PMD_TABLE_ORDER]!
ldr r6, =(_edata_loc - 1)
- add r0, r0, #1 << PMD_ORDER
- add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
+ add r0, r0, #1 << PMD_TABLE_ORDER
+ add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_TABLE_ORDER)
1: cmp r0, r6
add r3, r3, #1 << SECTION_SHIFT
- strls r3, [r0], #1 << PMD_ORDER
+ strls r3, [r0], #1 << PMD_TABLE_ORDER
bls 1b
#endif
@@ -286,10 +286,10 @@ __create_page_tables:
*/
mov r0, r2, lsr #SECTION_SHIFT
cmp r2, #0
- ldrne r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER)
+ ldrne r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_TABLE_ORDER)
addne r3, r3, r4
orrne r6, r7, r0, lsl #SECTION_SHIFT
- strne r6, [r3], #1 << PMD_ORDER
+ strne r6, [r3], #1 << PMD_TABLE_ORDER
addne r6, r6, #1 << SECTION_SHIFT
strne r6, [r3]
@@ -308,7 +308,7 @@ __create_page_tables:
addruart r7, r3, r0
mov r3, r3, lsr #SECTION_SHIFT
- mov r3, r3, lsl #PMD_ORDER
+ mov r3, r3, lsl #PMD_TABLE_ORDER
add r0, r4, r3
mov r3, r7, lsr #SECTION_SHIFT
@@ -338,7 +338,7 @@ __create_page_tables:
* If we're using the NetWinder or CATS, we also need to map
* in the 16550-type serial port for the debug messages
*/
- add r0, r4, #0xff000000 >> (SECTION_SHIFT - PMD_ORDER)
+ add r0, r4, #0xff000000 >> (SECTION_SHIFT - PMD_TABLE_ORDER)
orr r3, r7, #0x7c000000
str r3, [r0]
#endif
@@ -348,10 +348,10 @@ __create_page_tables:
* Similar reasons here - for debug. This is
* only for Acorn RiscPC architectures.
*/
- add r0, r4, #0x02000000 >> (SECTION_SHIFT - PMD_ORDER)
+ add r0, r4, #0x02000000 >> (SECTION_SHIFT - PMD_TABLE_ORDER)
orr r3, r7, #0x02000000
str r3, [r0]
- add r0, r4, #0xd8000000 >> (SECTION_SHIFT - PMD_ORDER)
+ add r0, r4, #0xd8000000 >> (SECTION_SHIFT - PMD_TABLE_ORDER)
str r3, [r0]
#endif
#endif
--
2.30.2
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH 2/3] mips: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 13:46 [PATCH 0/3] Make PMD_ORDER generically available Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER Matthew Wilcox (Oracle)
@ 2021-07-15 13:46 ` Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 3/3] parisc: " Matthew Wilcox (Oracle)
2021-07-15 16:28 ` [PATCH 0/3] Make PMD_ORDER generically available Helge Deller
3 siblings, 0 replies; 10+ messages in thread
From: Matthew Wilcox (Oracle) @ 2021-07-15 13:46 UTC (permalink / raw)
To: linux-arch, linux-parisc, linux-mips, linux-arm-kernel
Cc: Matthew Wilcox (Oracle), linux-kernel
This is the order of the page table allocation, not the order of a PMD.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
arch/mips/include/asm/pgalloc.h | 2 +-
arch/mips/include/asm/pgtable-32.h | 2 +-
arch/mips/include/asm/pgtable-64.h | 18 +++++++++---------
arch/mips/kernel/asm-offsets.c | 2 +-
4 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index 4b2567d6b2df..795e9e2219c9 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -61,7 +61,7 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
pmd_t *pmd = NULL;
struct page *pg;
- pg = alloc_pages(GFP_KERNEL | __GFP_ACCOUNT, PMD_ORDER);
+ pg = alloc_pages(GFP_KERNEL | __GFP_ACCOUNT, PMD_TABLE_ORDER);
if (pg) {
pgtable_pmd_page_ctor(pg);
pmd = (pmd_t *)page_address(pg);
diff --git a/arch/mips/include/asm/pgtable-32.h b/arch/mips/include/asm/pgtable-32.h
index 95df9c293d8d..8d57bd5b0b94 100644
--- a/arch/mips/include/asm/pgtable-32.h
+++ b/arch/mips/include/asm/pgtable-32.h
@@ -82,7 +82,7 @@ extern int add_temporary_entry(unsigned long entrylo0, unsigned long entrylo1,
#define PGD_ORDER (__PGD_ORDER >= 0 ? __PGD_ORDER : 0)
#define PUD_ORDER aieeee_attempt_to_allocate_pud
-#define PMD_ORDER aieeee_attempt_to_allocate_pmd
+#define PMD_TABLE_ORDER aieeee_attempt_to_allocate_pmd
#define PTE_ORDER 0
#define PTRS_PER_PGD (USER_PTRS_PER_PGD * 2)
diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 41921acdc9d8..ae0d5a09064d 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -51,12 +51,12 @@
#define PMD_MASK (~(PMD_SIZE-1))
# ifdef __PAGETABLE_PUD_FOLDED
-# define PGDIR_SHIFT (PMD_SHIFT + (PAGE_SHIFT + PMD_ORDER - 3))
+# define PGDIR_SHIFT (PMD_SHIFT + (PAGE_SHIFT + PMD_TABLE_ORDER - 3))
# endif
#endif
#ifndef __PAGETABLE_PUD_FOLDED
-#define PUD_SHIFT (PMD_SHIFT + (PAGE_SHIFT + PMD_ORDER - 3))
+#define PUD_SHIFT (PMD_SHIFT + (PAGE_SHIFT + PMD_TABLE_ORDER - 3))
#define PUD_SIZE (1UL << PUD_SHIFT)
#define PUD_MASK (~(PUD_SIZE-1))
#define PGDIR_SHIFT (PUD_SHIFT + (PAGE_SHIFT + PUD_ORDER - 3))
@@ -91,13 +91,13 @@
# define PGD_ORDER 1
# define PUD_ORDER aieeee_attempt_to_allocate_pud
# endif
-#define PMD_ORDER 0
+#define PMD_TABLE_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_8KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
-#define PMD_ORDER 0
+#define PMD_TABLE_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_16KB
@@ -107,22 +107,22 @@
#define PGD_ORDER 0
#endif
#define PUD_ORDER aieeee_attempt_to_allocate_pud
-#define PMD_ORDER 0
+#define PMD_TABLE_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_32KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
-#define PMD_ORDER 0
+#define PMD_TABLE_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_64KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#ifdef CONFIG_MIPS_VA_BITS_48
-#define PMD_ORDER 0
+#define PMD_TABLE_ORDER 0
#else
-#define PMD_ORDER aieeee_attempt_to_allocate_pmd
+#define PMD_TABLE_ORDER aieeee_attempt_to_allocate_pmd
#endif
#define PTE_ORDER 0
#endif
@@ -132,7 +132,7 @@
#define PTRS_PER_PUD ((PAGE_SIZE << PUD_ORDER) / sizeof(pud_t))
#endif
#ifndef __PAGETABLE_PMD_FOLDED
-#define PTRS_PER_PMD ((PAGE_SIZE << PMD_ORDER) / sizeof(pmd_t))
+#define PTRS_PER_PMD ((PAGE_SIZE << PMD_TABLE_ORDER) / sizeof(pmd_t))
#endif
#define PTRS_PER_PTE ((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))
diff --git a/arch/mips/kernel/asm-offsets.c b/arch/mips/kernel/asm-offsets.c
index 04ca75278f02..d6b89080d245 100644
--- a/arch/mips/kernel/asm-offsets.c
+++ b/arch/mips/kernel/asm-offsets.c
@@ -198,7 +198,7 @@ void output_mm_defines(void)
BLANK();
DEFINE(_PGD_ORDER, PGD_ORDER);
#ifndef __PAGETABLE_PMD_FOLDED
- DEFINE(_PMD_ORDER, PMD_ORDER);
+ DEFINE(_PMD_TABLE_ORDER, PMD_TABLE_ORDER);
#endif
DEFINE(_PTE_ORDER, PTE_ORDER);
BLANK();
--
2.30.2
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH 3/3] parisc: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 13:46 [PATCH 0/3] Make PMD_ORDER generically available Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 2/3] mips: " Matthew Wilcox (Oracle)
@ 2021-07-15 13:46 ` Matthew Wilcox (Oracle)
2021-07-15 16:28 ` [PATCH 0/3] Make PMD_ORDER generically available Helge Deller
3 siblings, 0 replies; 10+ messages in thread
From: Matthew Wilcox (Oracle) @ 2021-07-15 13:46 UTC (permalink / raw)
To: linux-arch, linux-parisc, linux-mips, linux-arm-kernel
Cc: Matthew Wilcox (Oracle), linux-kernel
This is the order of the page table allocation, not the order of a PMD.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
arch/parisc/include/asm/pgalloc.h | 6 +++---
arch/parisc/include/asm/pgtable.h | 4 ++--
arch/parisc/mm/init.c | 4 ++--
3 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
index 6a7e98e71f1d..54b63374579b 100644
--- a/arch/parisc/include/asm/pgalloc.h
+++ b/arch/parisc/include/asm/pgalloc.h
@@ -48,15 +48,15 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
{
pmd_t *pmd;
- pmd = (pmd_t *)__get_free_pages(GFP_PGTABLE_KERNEL, PMD_ORDER);
+ pmd = (pmd_t *)__get_free_pages(GFP_PGTABLE_KERNEL, PMD_TABLE_ORDER);
if (likely(pmd))
- memset ((void *)pmd, 0, PAGE_SIZE << PMD_ORDER);
+ memset ((void *)pmd, 0, PAGE_SIZE << PMD_TABLE_ORDER);
return pmd;
}
static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
{
- free_pages((unsigned long)pmd, PMD_ORDER);
+ free_pages((unsigned long)pmd, PMD_TABLE_ORDER);
}
#endif
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 43937af127b1..7badd872f05a 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -112,7 +112,7 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
#define KERNEL_INITIAL_SIZE (1 << KERNEL_INITIAL_ORDER)
#if CONFIG_PGTABLE_LEVELS == 3
-#define PMD_ORDER 1
+#define PMD_TABLE_ORDER 1
#define PGD_ORDER 0
#else
#define PGD_ORDER 1
@@ -131,7 +131,7 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
#define PMD_SHIFT (PLD_SHIFT + BITS_PER_PTE)
#define PMD_SIZE (1UL << PMD_SHIFT)
#define PMD_MASK (~(PMD_SIZE-1))
-#define BITS_PER_PMD (PAGE_SHIFT + PMD_ORDER - BITS_PER_PMD_ENTRY)
+#define BITS_PER_PMD (PAGE_SHIFT + PMD_TABLE_ORDER - BITS_PER_PMD_ENTRY)
#define PTRS_PER_PMD (1UL << BITS_PER_PMD)
#else
#define BITS_PER_PMD 0
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 591a4e939415..3f7d6d5b56ac 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -378,8 +378,8 @@ static void __init map_pages(unsigned long start_vaddr,
#if CONFIG_PGTABLE_LEVELS == 3
if (pud_none(*pud)) {
- pmd = memblock_alloc(PAGE_SIZE << PMD_ORDER,
- PAGE_SIZE << PMD_ORDER);
+ pmd = memblock_alloc(PAGE_SIZE << PMD_TABLE_ORDER,
+ PAGE_SIZE << PMD_TABLE_ORDER);
if (!pmd)
panic("pmd allocation failed.\n");
pud_populate(NULL, pud, pmd);
--
2.30.2
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH 0/3] Make PMD_ORDER generically available
2021-07-15 13:46 [PATCH 0/3] Make PMD_ORDER generically available Matthew Wilcox (Oracle)
` (2 preceding siblings ...)
2021-07-15 13:46 ` [PATCH 3/3] parisc: " Matthew Wilcox (Oracle)
@ 2021-07-15 16:28 ` Helge Deller
2021-07-15 16:38 ` Matthew Wilcox
3 siblings, 1 reply; 10+ messages in thread
From: Helge Deller @ 2021-07-15 16:28 UTC (permalink / raw)
To: Matthew Wilcox (Oracle),
linux-arch, linux-parisc, linux-mips, linux-arm-kernel
Cc: linux-kernel
On 7/15/21 3:46 PM, Matthew Wilcox (Oracle) wrote:
> These three architectures each define PMD_ORDER to mean "the order of
> an allocation for a PMD table", but logically PMD_ORDER should be the
> order of a PMD allocation, ie (PMD_SHIFT - PAGE_SHIFT) as DAX defines it.
Some architectures do have PGD_ORDER, PUD_ORDER and PTE_ORDER as well.
If you rename PMD_ORDER, IMHO the others should be renamed too.
Why not simply rename "PMD_ORDER" in fs/dax.c to e.g.
#define DAX_PMD_SHIFT (PMD_SHIFT - PAGE_SHIFT)
and use that inside the dax filesystem code?
Helge
> Could each architecture maintainer please apply the appropriate patch
> to their respective trees?
>
> Matthew Wilcox (Oracle) (3):
> arm: Rename PMD_ORDER to PMD_TABLE_ORDER
> mips: Rename PMD_ORDER to PMD_TABLE_ORDER
> parisc: Rename PMD_ORDER to PMD_TABLE_ORDER
>
> arch/arm/kernel/head.S | 34 +++++++++++++++---------------
> arch/mips/include/asm/pgalloc.h | 2 +-
> arch/mips/include/asm/pgtable-32.h | 2 +-
> arch/mips/include/asm/pgtable-64.h | 18 ++++++++--------
> arch/mips/kernel/asm-offsets.c | 2 +-
> arch/parisc/include/asm/pgalloc.h | 6 +++---
> arch/parisc/include/asm/pgtable.h | 4 ++--
> arch/parisc/mm/init.c | 4 ++--
> 8 files changed, 36 insertions(+), 36 deletions(-)
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 0/3] Make PMD_ORDER generically available
2021-07-15 16:28 ` [PATCH 0/3] Make PMD_ORDER generically available Helge Deller
@ 2021-07-15 16:38 ` Matthew Wilcox
0 siblings, 0 replies; 10+ messages in thread
From: Matthew Wilcox @ 2021-07-15 16:38 UTC (permalink / raw)
To: Helge Deller
Cc: linux-arch, linux-parisc, linux-mips, linux-arm-kernel, linux-kernel
On Thu, Jul 15, 2021 at 06:28:42PM +0200, Helge Deller wrote:
> On 7/15/21 3:46 PM, Matthew Wilcox (Oracle) wrote:
> > These three architectures each define PMD_ORDER to mean "the order of
> > an allocation for a PMD table", but logically PMD_ORDER should be the
> > order of a PMD allocation, ie (PMD_SHIFT - PAGE_SHIFT) as DAX defines it.
>
> Some architectures do have PGD_ORDER, PUD_ORDER and PTE_ORDER as well.
> If you rename PMD_ORDER, IMHO the others should be renamed too.
>
> Why not simply rename "PMD_ORDER" in fs/dax.c to e.g.
> #define DAX_PMD_SHIFT (PMD_SHIFT - PAGE_SHIFT)
> and use that inside the dax filesystem code?
Because that's wrong. PMD order is clearly the order of a PMD page,
not the order of a PMD table.
I'm sure the others should also be renamed, but this is the one which
is causing me pain today.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 13:46 ` [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER Matthew Wilcox (Oracle)
@ 2021-07-15 16:47 ` Russell King (Oracle)
2021-07-15 18:10 ` Matthew Wilcox
0 siblings, 1 reply; 10+ messages in thread
From: Russell King (Oracle) @ 2021-07-15 16:47 UTC (permalink / raw)
To: Matthew Wilcox (Oracle)
Cc: linux-arch, linux-parisc, linux-mips, linux-arm-kernel, linux-kernel
On Thu, Jul 15, 2021 at 02:46:10PM +0100, Matthew Wilcox (Oracle) wrote:
> This is the order of the page table allocation, not the order of a PMD.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> arch/arm/kernel/head.S | 34 +++++++++++++++++-----------------
> 1 file changed, 17 insertions(+), 17 deletions(-)
>
> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
> index 9eb0b4dbcc12..6da39a1d70ba 100644
> --- a/arch/arm/kernel/head.S
> +++ b/arch/arm/kernel/head.S
> @@ -38,10 +38,10 @@
> #ifdef CONFIG_ARM_LPAE
> /* LPAE requires an additional page for the PGD */
> #define PG_DIR_SIZE 0x5000
> -#define PMD_ORDER 3
> +#define PMD_TABLE_ORDER 3
> #else
> #define PG_DIR_SIZE 0x4000
> -#define PMD_ORDER 2
> +#define PMD_TABLE_ORDER 2
I think PMD_ENTRY_ORDER would make more sense here - this is the
power-of-2 of an individual PMD entry, not of the entire table.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 16:47 ` Russell King (Oracle)
@ 2021-07-15 18:10 ` Matthew Wilcox
2021-07-15 18:37 ` Russell King (Oracle)
0 siblings, 1 reply; 10+ messages in thread
From: Matthew Wilcox @ 2021-07-15 18:10 UTC (permalink / raw)
To: Russell King (Oracle)
Cc: linux-arch, linux-parisc, linux-mips, linux-arm-kernel, linux-kernel
On Thu, Jul 15, 2021 at 05:47:41PM +0100, Russell King (Oracle) wrote:
> On Thu, Jul 15, 2021 at 02:46:10PM +0100, Matthew Wilcox (Oracle) wrote:
> > This is the order of the page table allocation, not the order of a PMD.
> > -#define PMD_ORDER 3
> > +#define PMD_TABLE_ORDER 3
> > #else
> > #define PG_DIR_SIZE 0x4000
> > -#define PMD_ORDER 2
> > +#define PMD_TABLE_ORDER 2
>
> I think PMD_ENTRY_ORDER would make more sense here - this is the
> power-of-2 of an individual PMD entry, not of the entire table.
But ... we have two kinds of PMD entries. We have the direct entry that
points to a 1-16MB sized chunk of memory, and we have the table entry that
points to a 4k-32k chunk of memory that contains PTEs. So I don't think
calling it 'entry' order actually disambiguates anything. That's why
I went with 'table' -- I can't think of anything else to call it!
PMD_PTE_ARRAY_ORDER doesn't seem like an improvement to me ...
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 18:10 ` Matthew Wilcox
@ 2021-07-15 18:37 ` Russell King (Oracle)
2021-07-15 19:16 ` Matthew Wilcox
0 siblings, 1 reply; 10+ messages in thread
From: Russell King (Oracle) @ 2021-07-15 18:37 UTC (permalink / raw)
To: Matthew Wilcox
Cc: linux-arch, linux-parisc, linux-mips, linux-arm-kernel, linux-kernel
On Thu, Jul 15, 2021 at 07:10:54PM +0100, Matthew Wilcox wrote:
> On Thu, Jul 15, 2021 at 05:47:41PM +0100, Russell King (Oracle) wrote:
> > On Thu, Jul 15, 2021 at 02:46:10PM +0100, Matthew Wilcox (Oracle) wrote:
> > > This is the order of the page table allocation, not the order of a PMD.
> > > -#define PMD_ORDER 3
> > > +#define PMD_TABLE_ORDER 3
> > > #else
> > > #define PG_DIR_SIZE 0x4000
> > > -#define PMD_ORDER 2
> > > +#define PMD_TABLE_ORDER 2
> >
> > I think PMD_ENTRY_ORDER would make more sense here - this is the
> > power-of-2 of an individual PMD entry, not of the entire table.
>
> But ... we have two kinds of PMD entries. We have the direct entry that
> points to a 1-16MB sized chunk of memory, and we have the table entry that
> points to a 4k-32k chunk of memory that contains PTEs. So I don't think
> calling it 'entry' order actually disambiguates anything. That's why
> I went with 'table' -- I can't think of anything else to call it!
> PMD_PTE_ARRAY_ORDER doesn't seem like an improvement to me ...
There may be two kinds of PMD entries, but that isn't relevant here.
Going back to the original terminology, 1 << PMD_ORDER here is the
size of each PMD entry. It doesn't have anything to do with how much
memory is being mapped by each entry.
I think what is confusing you is stuff like:
add r0, r4, #KERNEL_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
r4 is the base address of the page tables, and r0 is the address of
the entry we want to manipulate for "KERNEL_OFFSET" - which is the
virtual address. 1 << SECTION_SHIFT is how much memory each entry
maps (and this is fixed here - there's no variability as you suggest
above.)
Effectively, the calculation above is:
index = KERNEL_OFFSET >> SECTION_SHIFT;
pmd_entry_size = 1 << PMD_ORDER;
r0 = base + index * pmd_entry_size;
but in a single instruction as we can be sure that KERNEL_OFFSET will
have zeros as the low bits after shifting by SECTION_SHIFT - PMD_ORDER.
Hope this helps to explain what this PMD_ORDER is actually doing here.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER
2021-07-15 18:37 ` Russell King (Oracle)
@ 2021-07-15 19:16 ` Matthew Wilcox
0 siblings, 0 replies; 10+ messages in thread
From: Matthew Wilcox @ 2021-07-15 19:16 UTC (permalink / raw)
To: Russell King (Oracle)
Cc: linux-arch, linux-parisc, linux-mips, linux-arm-kernel, linux-kernel
On Thu, Jul 15, 2021 at 07:37:27PM +0100, Russell King (Oracle) wrote:
> On Thu, Jul 15, 2021 at 07:10:54PM +0100, Matthew Wilcox wrote:
> > On Thu, Jul 15, 2021 at 05:47:41PM +0100, Russell King (Oracle) wrote:
> > > On Thu, Jul 15, 2021 at 02:46:10PM +0100, Matthew Wilcox (Oracle) wrote:
> > > > This is the order of the page table allocation, not the order of a PMD.
> > > > -#define PMD_ORDER 3
> > > > +#define PMD_TABLE_ORDER 3
> > > > #else
> > > > #define PG_DIR_SIZE 0x4000
> > > > -#define PMD_ORDER 2
> > > > +#define PMD_TABLE_ORDER 2
> > >
> > > I think PMD_ENTRY_ORDER would make more sense here - this is the
> > > power-of-2 of an individual PMD entry, not of the entire table.
> >
> > But ... we have two kinds of PMD entries. We have the direct entry that
> > points to a 1-16MB sized chunk of memory, and we have the table entry that
> > points to a 4k-32k chunk of memory that contains PTEs. So I don't think
> > calling it 'entry' order actually disambiguates anything. That's why
> > I went with 'table' -- I can't think of anything else to call it!
> > PMD_PTE_ARRAY_ORDER doesn't seem like an improvement to me ...
>
> There may be two kinds of PMD entries, but that isn't relevant here.
> Going back to the original terminology, 1 << PMD_ORDER here is the
> size of each PMD entry. It doesn't have anything to do with how much
> memory is being mapped by each entry.
Oh. Oh! So, 'order' is usually a shift that is _added on to_ the
PAGE_SHIFT in order to find how many bytes are in question. See
include/asm-generic/getorder.h.
Now, PMD_SHIFT is already in use, but perhaps what is meant here is
PMD_ENTRY_SHIFT?
> I think what is confusing you is stuff like:
>
> add r0, r4, #KERNEL_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
>
> r4 is the base address of the page tables, and r0 is the address of
> the entry we want to manipulate for "KERNEL_OFFSET" - which is the
> virtual address. 1 << SECTION_SHIFT is how much memory each entry
> maps (and this is fixed here - there's no variability as you suggest
> above.)
(the variability I intended above was more to accommodate architectural
differences; I hate to use x86-specific numbers like 4KiB and 2MiB)
> Effectively, the calculation above is:
>
> index = KERNEL_OFFSET >> SECTION_SHIFT;
> pmd_entry_size = 1 << PMD_ORDER;
> r0 = base + index * pmd_entry_size;
>
> but in a single instruction as we can be sure that KERNEL_OFFSET will
> have zeros as the low bits after shifting by SECTION_SHIFT - PMD_ORDER.
>
> Hope this helps to explain what this PMD_ORDER is actually doing here.
Thank you, yes, I was terminally confused.
^ permalink raw reply [flat|nested] 10+ messages in thread
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Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-15 13:46 [PATCH 0/3] Make PMD_ORDER generically available Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 1/3] arm: Rename PMD_ORDER to PMD_TABLE_ORDER Matthew Wilcox (Oracle)
2021-07-15 16:47 ` Russell King (Oracle)
2021-07-15 18:10 ` Matthew Wilcox
2021-07-15 18:37 ` Russell King (Oracle)
2021-07-15 19:16 ` Matthew Wilcox
2021-07-15 13:46 ` [PATCH 2/3] mips: " Matthew Wilcox (Oracle)
2021-07-15 13:46 ` [PATCH 3/3] parisc: " Matthew Wilcox (Oracle)
2021-07-15 16:28 ` [PATCH 0/3] Make PMD_ORDER generically available Helge Deller
2021-07-15 16:38 ` Matthew Wilcox
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