Re: [Xen-devel] [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

2016-05-12 Thread Julien Grall 



On 12/05/16 12:30, Peng Fan wrote:

Hi Julien,

On Thu, May 12, 2016 at 11:48:30AM +0100, Julien Grall wrote:

Hi Peng,

On 12/05/16 07:36, Peng Fan wrote:

To ARM64, "frametable_size >> SECOND_SHIFT" means the number
of second level entries, not the number of second level pages.

"DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES)"
is the correct way to calculate the second level pages needed
for frametable mapping.


Good catch!


Signed-off-by: Peng Fan 
Cc: Stefano Stabellini 
Cc: Julien Grall 
---
  xen/arch/arm/mm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 0a4f845..7c7f8e9 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -767,7 +767,7 @@ void __init setup_frametable_mappings(paddr_t ps, paddr_t 
pe)
  base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-12));

  #ifdef CONFIG_ARM_64
-nr_second = frametable_size >> SECOND_SHIFT;
+nr_second = DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES);



I think the following would be clearer:

ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT;


Agree.



This would also benefit a comment to explain that second level of page table
are populating.


Do you mean I need to add a comment for the upper code?


Yes.



For the commit log, I would like to change to this:
"
To ARM64, "frametable_size >> SECOND_SHIFT" means the number


On ARM64,

s/means/computes/



of second level entries, not the number of second level pages.

"ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT" which means


s/means/computes/


the number of the first level entries(the number of second level pages),


missing space after "entries"


is the correct one that should be used.
"


Regards,

--
Julien Grall

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Re: [Xen-devel] [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

2016-05-12 Thread Peng Fan 
Hi Julien,

On Thu, May 12, 2016 at 11:48:30AM +0100, Julien Grall wrote:
>Hi Peng,
>
>On 12/05/16 07:36, Peng Fan wrote:
>>To ARM64, "frametable_size >> SECOND_SHIFT" means the number
>>of second level entries, not the number of second level pages.
>>
>>"DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES)"
>>is the correct way to calculate the second level pages needed
>>for frametable mapping.
>
>Good catch!
>
>>Signed-off-by: Peng Fan 
>>Cc: Stefano Stabellini 
>>Cc: Julien Grall 
>>---
>>  xen/arch/arm/mm.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>>diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
>>index 0a4f845..7c7f8e9 100644
>>--- a/xen/arch/arm/mm.c
>>+++ b/xen/arch/arm/mm.c
>>@@ -767,7 +767,7 @@ void __init setup_frametable_mappings(paddr_t ps, paddr_t 
>>pe)
>>  base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-12));
>>
>>  #ifdef CONFIG_ARM_64
>>-nr_second = frametable_size >> SECOND_SHIFT;
>>+nr_second = DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES);
>
>
>I think the following would be clearer:
>
>ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT;

Agree.

>
>This would also benefit a comment to explain that second level of page table
>are populating.

Do you mean I need to add a comment for the upper code?

For the commit log, I would like to change to this:
"
To ARM64, "frametable_size >> SECOND_SHIFT" means the number
of second level entries, not the number of second level pages.

"ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT" which means
the number of the first level entries(the number of second level pages),
is the correct one that should be used.
"
How do you think?

Thanks,
Peng.
>
>>  second_base = alloc_boot_pages(nr_second, 1);
>>  second = mfn_to_virt(second_base);
>>  for ( i = 0; i < nr_second; i++ )
>>
>
>Regards,
>
>-- 
>Julien Grall

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Re: [Xen-devel] [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

2016-05-12 Thread Julien Grall 

Hi Peng,

On 12/05/16 07:36, Peng Fan wrote:

To ARM64, "frametable_size >> SECOND_SHIFT" means the number
of second level entries, not the number of second level pages.

"DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES)"
is the correct way to calculate the second level pages needed
for frametable mapping.


Good catch!


Signed-off-by: Peng Fan 
Cc: Stefano Stabellini 
Cc: Julien Grall 
---
  xen/arch/arm/mm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 0a4f845..7c7f8e9 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -767,7 +767,7 @@ void __init setup_frametable_mappings(paddr_t ps, paddr_t 
pe)
  base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-12));

  #ifdef CONFIG_ARM_64
-nr_second = frametable_size >> SECOND_SHIFT;
+nr_second = DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES);



I think the following would be clearer:

ROUNDUP(frametable_size, FIRST_SIZE) >> FIRST_SHIFT;

This would also benefit a comment to explain that second level of page 
table are populating.



  second_base = alloc_boot_pages(nr_second, 1);
  second = mfn_to_virt(second_base);
  for ( i = 0; i < nr_second; i++ )



Regards,

--
Julien Grall

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[Xen-devel] [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings

2016-05-12 Thread Peng Fan 
To ARM64, "frametable_size >> SECOND_SHIFT" means the number
of second level entries, not the number of second level pages.

"DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES)"
is the correct way to calculate the second level pages needed
for frametable mapping.

Signed-off-by: Peng Fan 
Cc: Stefano Stabellini 
Cc: Julien Grall 
---
 xen/arch/arm/mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 0a4f845..7c7f8e9 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -767,7 +767,7 @@ void __init setup_frametable_mappings(paddr_t ps, paddr_t 
pe)
 base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-12));
 
 #ifdef CONFIG_ARM_64
-nr_second = frametable_size >> SECOND_SHIFT;
+nr_second = DIV_ROUND_UP(frametable_size >> SECOND_SHIFT, LPAE_ENTRIES);
 second_base = alloc_boot_pages(nr_second, 1);
 second = mfn_to_virt(second_base);
 for ( i = 0; i < nr_second; i++ )
-- 
2.6.2


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