Re: [PATCH v2] arm: improve non-section-aligned low memory mapping
On Wed, May 06, 2015 at 11:32:49AM +0100, Russell King - ARM Linux wrote:
> On Sun, Apr 26, 2015 at 04:47:08PM +0800, Min-Hua Chen wrote:
> > @@ -1384,6 +1351,15 @@ static void __init map_lowmem(void)
> > create_mapping();
> > }
> > }
> > +
> > + /*
> > +* Find the first section-aligned memblock and set
> > +* memblock_limit at it.
> > +*/
> > + if (!section_memblock_limit && !(end & ~SECTION_MASK)) {
> > + section_memblock_limit = end;
> > + memblock_set_current_limit(section_memblock_limit);
> > + }
>
> I've suggested an alternative solution to this (which just means changing
> the alignment of the memblock limit to 2x SECTION_SIZE).
Sorry I do not understand your suggestion very well. Do you mean the
alignment check should be 2X SECTION_SIZE?
if (!section_memblock_limit && !(end & (2 * SECTION_SIZE - 1))) {
I found that this solution is based on the fact that the first memory block is
always SECTION_SIZE-aligned. So we do not have to check the
alignment of the first memblock:
if (!section_memblock_limit)) {
section_memblock_limit = end;
memblock_set_current_limit(section_memblock_limit);
}
> --
> FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
> according to speedtest.net.
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Re: [PATCH v2] arm: improve non-section-aligned low memory mapping
On Wed, May 06, 2015 at 11:32:49AM +0100, Russell King - ARM Linux wrote:
On Sun, Apr 26, 2015 at 04:47:08PM +0800, Min-Hua Chen wrote:
@@ -1384,6 +1351,15 @@ static void __init map_lowmem(void)
create_mapping(map);
}
}
+
+ /*
+* Find the first section-aligned memblock and set
+* memblock_limit at it.
+*/
+ if (!section_memblock_limit !(end ~SECTION_MASK)) {
+ section_memblock_limit = end;
+ memblock_set_current_limit(section_memblock_limit);
+ }
I've suggested an alternative solution to this (which just means changing
the alignment of the memblock limit to 2x SECTION_SIZE).
Sorry I do not understand your suggestion very well. Do you mean the
alignment check should be 2X SECTION_SIZE?
if (!section_memblock_limit !(end (2 * SECTION_SIZE - 1))) {
I found that this solution is based on the fact that the first memory block is
always SECTION_SIZE-aligned. So we do not have to check the
alignment of the first memblock:
if (!section_memblock_limit)) {
section_memblock_limit = end;
memblock_set_current_limit(section_memblock_limit);
}
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2] arm: improve non-section-aligned low memory mapping
On Sun, Apr 26, 2015 at 04:47:08PM +0800, Min-Hua Chen wrote:
> @@ -1384,6 +1351,15 @@ static void __init map_lowmem(void)
> create_mapping();
> }
> }
> +
> + /*
> + * Find the first section-aligned memblock and set
> + * memblock_limit at it.
> + */
> + if (!section_memblock_limit && !(end & ~SECTION_MASK)) {
> + section_memblock_limit = end;
> + memblock_set_current_limit(section_memblock_limit);
> + }
I've suggested an alternative solution to this (which just means changing
the alignment of the memblock limit to 2x SECTION_SIZE).
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2] arm: improve non-section-aligned low memory mapping
On Sun, Apr 26, 2015 at 04:47:08PM +0800, Min-Hua Chen wrote:
@@ -1384,6 +1351,15 @@ static void __init map_lowmem(void)
create_mapping(map);
}
}
+
+ /*
+ * Find the first section-aligned memblock and set
+ * memblock_limit at it.
+ */
+ if (!section_memblock_limit !(end ~SECTION_MASK)) {
+ section_memblock_limit = end;
+ memblock_set_current_limit(section_memblock_limit);
+ }
I've suggested an alternative solution to this (which just means changing
the alignment of the memblock limit to 2x SECTION_SIZE).
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH v2] arm: improve non-section-aligned low memory mapping
Fix space errors.
In current design, the memblock.current_limit is set to
a section-aligned value in sanity_check_meminfo().
However, the section-aligned memblock may become non-section-aligned
after arm_memblock_init(). For example, the first section-aligned
memblock is 0x-0x0100 and sanity_check_meminfo sets
current_limit to 0x0100. After arm_memblock_init, two memory blocks
[0x00c0 - 0x00d0] and [0x00ff - 0x0100] are reserved
by memblock_reserve() and make the original memory block
[0x-0x0100] becomes:
[0x-0x00c0]
[0x00d0-0x00ff]
When creating the low memory mapping for [0x00d0-0x00ff],
since the memory block is non-section-aligned, it will need to create
a second level page table. But the current_limit is set to 0x0100,
and it's possible to allocate a unmapped memory block.
call flow:
setup_arch
+ sanity_check_meminfo
+ arm_memblock_init
+ paging_init
+ map_lowmem
+ bootmem_init
Move the memblock_set_current_limit logic to map_lowmem(), we point
the memblock current_limit to the first section-aligned memblock block.
Since map_lowmem() is called after arm_memblock_init(), there is no way to
change memblock layout. So we can say that the first section-aligned limit
is valid during map_lowmem(). Hence fix the problem described above.
Another change is change the implementation of find_limits().
In commit: 1c2f87c22566cd057bc8cde10c37ae9da1a1bb76, the max_low is
set by memblock_get_current_limit(). However memblock.current_limit
can be changed by memblock_set_current_limit() anypoint before
find_limits().
It's better to use arm_lowmem_limit to be max_lowmem in two ways:
First, arm_lowmem_limit cannot be changed by a public API. Second, the
high_memory is set by arm_lowmem_limit and is a natural limit of
low memory area in bootmem_init().
thanks,
Min-Hua
Signed-off-by: Min-Hua Chen
---
arch/arm/mm/init.c |2 +-
arch/arm/mm/mmu.c | 44 ++--
2 files changed, 11 insertions(+), 35 deletions(-)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 2495c8c..6a618f9 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -138,7 +138,7 @@ void show_mem(unsigned int filter)
static void __init find_limits(unsigned long *min, unsigned long *max_low,
unsigned long *max_high)
{
- *max_low = PFN_DOWN(memblock_get_current_limit());
+ *max_low = PFN_DOWN(arm_lowmem_limit);
*min = PFN_UP(memblock_start_of_DRAM());
*max_high = PFN_DOWN(memblock_end_of_DRAM());
}
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 4e6ef89..dbc484d 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1068,7 +1068,6 @@ phys_addr_t arm_lowmem_limit __initdata = 0;
void __init sanity_check_meminfo(void)
{
- phys_addr_t memblock_limit = 0;
int highmem = 0;
phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1;
struct memblock_region *reg;
@@ -1110,43 +1109,10 @@ void __init sanity_check_meminfo(void)
else
arm_lowmem_limit = block_end;
}
-
- /*
-* Find the first non-section-aligned page, and point
-* memblock_limit at it. This relies on rounding the
-* limit down to be section-aligned, which happens at
-* the end of this function.
-*
-* With this algorithm, the start or end of almost any
-* bank can be non-section-aligned. The only exception
-* is that the start of the bank 0 must be section-
-* aligned, since otherwise memory would need to be
-* allocated when mapping the start of bank 0, which
-* occurs before any free memory is mapped.
-*/
- if (!memblock_limit) {
- if (!IS_ALIGNED(block_start, SECTION_SIZE))
- memblock_limit = block_start;
- else if (!IS_ALIGNED(block_end, SECTION_SIZE))
- memblock_limit = arm_lowmem_limit;
- }
-
}
}
high_memory = __va(arm_lowmem_limit - 1) + 1;
-
- /*
-* Round the memblock limit down to a section size. This
-* helps to ensure that we will allocate memory from the
-* last full section, which should be mapped.
-*/
- if (memblock_limit)
- memblock_limit = round_down(memblock_limit, SECTION_SIZE);
- if (!memblock_limit)
- memblock_limit = arm_lowmem_limit;
-
- memblock_set_current_limit(memblock_limit);
}
static inline void prepare_page_table(void)
@@ -1331,6
[PATCH v2] arm: improve non-section-aligned low memory mapping
Fix space errors.
In current design, the memblock.current_limit is set to
a section-aligned value in sanity_check_meminfo().
However, the section-aligned memblock may become non-section-aligned
after arm_memblock_init(). For example, the first section-aligned
memblock is 0x-0x0100 and sanity_check_meminfo sets
current_limit to 0x0100. After arm_memblock_init, two memory blocks
[0x00c0 - 0x00d0] and [0x00ff - 0x0100] are reserved
by memblock_reserve() and make the original memory block
[0x-0x0100] becomes:
[0x-0x00c0]
[0x00d0-0x00ff]
When creating the low memory mapping for [0x00d0-0x00ff],
since the memory block is non-section-aligned, it will need to create
a second level page table. But the current_limit is set to 0x0100,
and it's possible to allocate a unmapped memory block.
call flow:
setup_arch
+ sanity_check_meminfo
+ arm_memblock_init
+ paging_init
+ map_lowmem
+ bootmem_init
Move the memblock_set_current_limit logic to map_lowmem(), we point
the memblock current_limit to the first section-aligned memblock block.
Since map_lowmem() is called after arm_memblock_init(), there is no way to
change memblock layout. So we can say that the first section-aligned limit
is valid during map_lowmem(). Hence fix the problem described above.
Another change is change the implementation of find_limits().
In commit: 1c2f87c22566cd057bc8cde10c37ae9da1a1bb76, the max_low is
set by memblock_get_current_limit(). However memblock.current_limit
can be changed by memblock_set_current_limit() anypoint before
find_limits().
It's better to use arm_lowmem_limit to be max_lowmem in two ways:
First, arm_lowmem_limit cannot be changed by a public API. Second, the
high_memory is set by arm_lowmem_limit and is a natural limit of
low memory area in bootmem_init().
thanks,
Min-Hua
Signed-off-by: Min-Hua Chen orca.c...@gmail.com
---
arch/arm/mm/init.c |2 +-
arch/arm/mm/mmu.c | 44 ++--
2 files changed, 11 insertions(+), 35 deletions(-)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 2495c8c..6a618f9 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -138,7 +138,7 @@ void show_mem(unsigned int filter)
static void __init find_limits(unsigned long *min, unsigned long *max_low,
unsigned long *max_high)
{
- *max_low = PFN_DOWN(memblock_get_current_limit());
+ *max_low = PFN_DOWN(arm_lowmem_limit);
*min = PFN_UP(memblock_start_of_DRAM());
*max_high = PFN_DOWN(memblock_end_of_DRAM());
}
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 4e6ef89..dbc484d 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1068,7 +1068,6 @@ phys_addr_t arm_lowmem_limit __initdata = 0;
void __init sanity_check_meminfo(void)
{
- phys_addr_t memblock_limit = 0;
int highmem = 0;
phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1;
struct memblock_region *reg;
@@ -1110,43 +1109,10 @@ void __init sanity_check_meminfo(void)
else
arm_lowmem_limit = block_end;
}
-
- /*
-* Find the first non-section-aligned page, and point
-* memblock_limit at it. This relies on rounding the
-* limit down to be section-aligned, which happens at
-* the end of this function.
-*
-* With this algorithm, the start or end of almost any
-* bank can be non-section-aligned. The only exception
-* is that the start of the bank 0 must be section-
-* aligned, since otherwise memory would need to be
-* allocated when mapping the start of bank 0, which
-* occurs before any free memory is mapped.
-*/
- if (!memblock_limit) {
- if (!IS_ALIGNED(block_start, SECTION_SIZE))
- memblock_limit = block_start;
- else if (!IS_ALIGNED(block_end, SECTION_SIZE))
- memblock_limit = arm_lowmem_limit;
- }
-
}
}
high_memory = __va(arm_lowmem_limit - 1) + 1;
-
- /*
-* Round the memblock limit down to a section size. This
-* helps to ensure that we will allocate memory from the
-* last full section, which should be mapped.
-*/
- if (memblock_limit)
- memblock_limit = round_down(memblock_limit, SECTION_SIZE);
- if (!memblock_limit)
- memblock_limit = arm_lowmem_limit;
-
- memblock_set_current_limit(memblock_limit);
}
static inline void
