Subject: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32 CPUs

From: [email-masked] (Liu hua)
Date: Mon, 14 Apr 2014 20:28:56 +0800

? 2014/4/14 1:34, Nicolas Pitre ??:
> On Sun, 13 Apr 2014, Liu hua wrote:
> 
>> Hi Nicolas.
>>
>> Sure, your suggestion made my patch looks better. How about that :
>>
>> Thanks,
>> Liu Hua
> 
> There is something else that bothers me.
> 
>> +	unsigned long idx = __virt_to_fix(vaddr);
>> +	idx -= FIX_KMAP_BEGIN;
>> +	return *(fixmap_page_table + idx);
> 
> FIX_KMAP_BEGIN represents the starting point for mapping fixmap indices 
> to page table entries.  So here you should _add_ the 
> FIX_KMAP_BEGIN offset to the page table index not substract it.  
> Currently FIX_KMAP_BEGIN is defined to 0 but still.
> 
>> +}
>> +
>>  #ifdef CONFIG_DEBUG_HIGHMEM
>> -	BUG_ON(!pte_none(get_top_pte(vaddr)));
>> +	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
> 
> Ditto here.
> 
> In fact, this FIX_KMAP_BEGIN is only creating more confusing code for 
> nothing as we define it to 0 anyway, and it is not used by non 
> architecture specific code.  So I'd suggest you create a patch to be 
> applied before this one that simply gets rid of FIX_KMAP_BEGIN and 
> FIX_KMAP_END altogether.  We could reintroduce them back if ever they're 
> needed.
> 
> 
> Nicolas
> 
Hi Nicolas,

Yes, it seems that FIX_KMAP_BEGIN and FIX_KMAP_END are not as important for
ARM than that for other architectures (MIPS PowerPC x86), whose FIX_KMAP_BEGIN
is not 0. I will reminder this in my patch. Anyone who need them can get
imformantion there.

Now the new patchs are following. Maybe I sould resend the patch series
with a new tag. If It is time to do that. Can I add this information
"Reviewed-by: Nicolas Pitre <[email-masked]>" ?

Thanks,
Liu Hua.

-----------------patch 1-------------------------

Subject: [PATCH 1/2] ARM : fixmap : remove FIX_KMAP_BEGIN and FIX_KMAP_END

It seems that these two variables are not used by non
architecture specific code. And on ARM FIX_KMAP_BEGIN
equals zero; FIX_KMAP_END is totally not used by the
kernel.

This patch removes these two variables. The code will
become clear when I introduce a bugfix on fixmap mapping
region.

Signed-off-by: Liu Hua <[email-masked]>
---
 arch/arm/include/asm/fixmap.h | 12 ++++++++----
 arch/arm/mm/highmem.c         |  6 +++---
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index bbae919..8675bb9 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -17,9 +17,13 @@
 #define FIXADDR_TOP		0xfffe0000UL
 #define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)

-#define FIX_KMAP_BEGIN		0
-#define FIX_KMAP_END		(FIXADDR_SIZE >> PAGE_SHIFT)
-
+/* Notice : FIX_KMAP_END and FIX_KMAP_BEGIN are removed.
+ *
+ * Instead, using FIX_KMAP_NR_PTES to tell the pte number
+ * belonged to fixmap mapping region.
+ *
+ */
+#define FIX_KMAP_NR_PTES	(FIXADDR_SIZE >> PAGE_SHIFT)
 #define __fix_to_virt(x)	(FIXADDR_START + ((x) << PAGE_SHIFT))
 #define __virt_to_fix(x)	(((x) - FIXADDR_START) >> PAGE_SHIFT)

@@ -27,7 +31,7 @@ extern void __this_fixmap_does_not_exist(void);

 static inline unsigned long fix_to_virt(const unsigned int idx)
 {
-	if (idx >= FIX_KMAP_END)
+	if (idx >= FIX_KMAP_NR_PTES)
 		__this_fixmap_does_not_exist();
 	return __fix_to_virt(idx);
 }
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 21b9e1b..e05e8ad 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -63,7 +63,7 @@ void *kmap_atomic(struct page *page)
 	type = kmap_atomic_idx_push();

 	idx = type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	vaddr = __fix_to_virt(idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
 	/*
 	 * With debugging enabled, kunmap_atomic forces that entry to 0.
@@ -94,7 +94,7 @@ void __kunmap_atomic(void *kvaddr)
 		if (cache_is_vivt())
 			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
 #ifdef CONFIG_DEBUG_HIGHMEM
-		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+		BUG_ON(vaddr != __fix_to_virt(idx));
 		set_top_pte(vaddr, __pte(0));
 #else
 		(void) idx;  /* to kill a warning */
@@ -117,7 +117,7 @@ void *kmap_atomic_pfn(unsigned long pfn)

 	type = kmap_atomic_idx_push();
 	idx = type + KM_TYPE_NR * smp_processor_id();
-	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	vaddr = __fix_to_virt(idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
 	BUG_ON(!pte_none(get_top_pte(vaddr)));
 #endif
-- 
1.9.0

-----------------patch 2-------------------------

Subject: [PATCH 2/2] ARM : change fixmap mapping region to support 32 CPUs

In 32-bit ARM systems, the fixmap mapping region can support
no more than 14 CPUs(total: 896k; one CPU: 64K). And we can
configure NR_CPUS up to 32. So there is a mismatch.

This patch moves fixmapping region downwards to region
0xffc00000-0xffe00000 . Then the fixmap mapping region can
support up to 32 CPUs

Signed-off-by: Liu Hua <[email-masked]>
---
 Documentation/arm/memory.txt   |  2 +-
 arch/arm/include/asm/fixmap.h  | 16 ++--------------
 arch/arm/include/asm/highmem.h |  1 +
 arch/arm/mm/highmem.c          | 27 +++++++++++++++++++++------
 arch/arm/mm/mmu.c              |  4 ++++
 5 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/Documentation/arm/memory.txt b/Documentation/arm/memory.txt
index d74e8a5..256c5e0 100644
--- a/Documentation/arm/memory.txt
+++ b/Documentation/arm/memory.txt
@@ -41,7 +41,7 @@ fffe8000	fffeffff	DTCM mapping area for platforms with
 fffe0000	fffe7fff	ITCM mapping area for platforms with
 				ITCM mounted inside the CPU.

-fff00000	fffdffff	Fixmap mapping region.  Addresses provided
+fffc0000	ffdfffff	Fixmap mapping region.  Addresses provided
 				by fix_to_virt() will be located here.

 fee00000	feffffff	Mapping of PCI I/O space. This is a static
diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index 8675bb9..fb8a5a7 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -1,20 +1,8 @@
 #ifndef _ASM_FIXMAP_H
 #define _ASM_FIXMAP_H

-/*
- * Nothing too fancy for now.
- *
- * On ARM we already have well known fixed virtual addresses imposed by
- * the architecture such as the vector page which is located at 0xffff0000,
- * therefore a second level page table is already allocated covering
- * 0xfff00000 upwards.
- *
- * The cache flushing code in proc-xscale.S uses the virtual area between
- * 0xfffe0000 and 0xfffeffff.
- */
-
-#define FIXADDR_START		0xfff00000UL
-#define FIXADDR_TOP		0xfffe0000UL
+#define FIXADDR_START		0xffc00000UL
+#define FIXADDR_TOP		0xffe00000UL
 #define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)

 /* Notice : FIX_KMAP_END and FIX_KMAP_BEGIN are removed.
diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index 91b99ab..5355795 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -18,6 +18,7 @@
 	} while (0)

 extern pte_t *pkmap_page_table;
+extern pte_t *fixmap_page_table;

 extern void *kmap_high(struct page *page);
 extern void kunmap_high(struct page *page);
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index e05e8ad..45aeaac 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -18,6 +18,21 @@
 #include <asm/tlbflush.h>
 #include "mm.h"

+pte_t *fixmap_page_table;
+
+static inline void set_fixmap_pte(int idx, pte_t pte)
+{
+	unsigned long vaddr = __fix_to_virt(idx);
+	set_pte_ext(fixmap_page_table + idx, pte, 0);
+	local_flush_tlb_kernel_page(vaddr);
+}
+
+static inline pte_t get_fixmap_pte(unsigned long vaddr)
+{
+	unsigned long idx = __virt_to_fix(vaddr);
+	return *(fixmap_page_table + idx);
+}
+
 void *kmap(struct page *page)
 {
 	might_sleep();
@@ -69,14 +84,14 @@ void *kmap_atomic(struct page *page)
 	 * With debugging enabled, kunmap_atomic forces that entry to 0.
 	 * Make sure it was indeed properly unmapped.
 	 */
-	BUG_ON(!pte_none(get_top_pte(vaddr)));
+	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
 #endif
 	/*
 	 * When debugging is off, kunmap_atomic leaves the previous mapping
 	 * in place, so the contained TLB flush ensures the TLB is updated
 	 * with the new mapping.
 	 */
-	set_top_pte(vaddr, mk_pte(page, kmap_prot));
+	set_fixmap_pte(idx, mk_pte(page, kmap_prot));

 	return (void *)vaddr;
 }
@@ -95,7 +110,7 @@ void __kunmap_atomic(void *kvaddr)
 			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
 #ifdef CONFIG_DEBUG_HIGHMEM
 		BUG_ON(vaddr != __fix_to_virt(idx));
-		set_top_pte(vaddr, __pte(0));
+		set_fixmap_pte(idx, __pte(0));
 #else
 		(void) idx;  /* to kill a warning */
 #endif
@@ -119,9 +134,9 @@ void *kmap_atomic_pfn(unsigned long pfn)
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
-	BUG_ON(!pte_none(get_top_pte(vaddr)));
+	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
 #endif
-	set_top_pte(vaddr, pfn_pte(pfn, kmap_prot));
+	set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));

 	return (void *)vaddr;
 }
@@ -133,5 +148,5 @@ struct page *kmap_atomic_to_page(const void *ptr)
 	if (vaddr < FIXADDR_START)
 		return virt_to_page(ptr);

-	return pte_page(get_top_pte(vaddr));
+	return pte_page(get_fixmap_pte(vaddr));
 }
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index b68c6b2..09c0a16 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -35,6 +35,7 @@
 #include <asm/mach/arch.h>
 #include <asm/mach/map.h>
 #include <asm/mach/pci.h>
+#include <asm/fixmap.h>

 #include "mm.h"
 #include "tcm.h"
@@ -1359,6 +1360,9 @@ static void __init kmap_init(void)
 #ifdef CONFIG_HIGHMEM
 	pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
 		PKMAP_BASE, _PAGE_KERNEL_TABLE);
+
+	fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
+		FIXADDR_START, _PAGE_KERNEL_TABLE);
 #endif
 }

-- 
1.9.0