* [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings
@ 2016-05-12 6:36 Peng Fan
2016-05-12 10:48 ` Julien Grall
0 siblings, 1 reply; 4+ messages in thread
From: Peng Fan @ 2016-05-12 6:36 UTC (permalink / raw)
To: xen-devel, julien.grall, sstabellini; +Cc: van.freenix
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 <van.freenix@gmail.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
---
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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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings
2016-05-12 6:36 [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings Peng Fan
@ 2016-05-12 10:48 ` Julien Grall
2016-05-12 11:30 ` Peng Fan
0 siblings, 1 reply; 4+ messages in thread
From: Julien Grall @ 2016-05-12 10:48 UTC (permalink / raw)
To: Peng Fan, xen-devel, sstabellini
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 <van.freenix@gmail.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Julien Grall <julien.grall@arm.com>
> ---
> 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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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings
2016-05-12 10:48 ` Julien Grall
@ 2016-05-12 11:30 ` Peng Fan
2016-05-12 12:07 ` Julien Grall
0 siblings, 1 reply; 4+ messages in thread
From: Peng Fan @ 2016-05-12 11:30 UTC (permalink / raw)
To: Julien Grall; +Cc: sstabellini, xen-devel
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 <van.freenix@gmail.com>
>>Cc: Stefano Stabellini <sstabellini@kernel.org>
>>Cc: Julien Grall <julien.grall@arm.com>
>>---
>> 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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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings
2016-05-12 11:30 ` Peng Fan
@ 2016-05-12 12:07 ` Julien Grall
0 siblings, 0 replies; 4+ messages in thread
From: Julien Grall @ 2016-05-12 12:07 UTC (permalink / raw)
To: Peng Fan; +Cc: sstabellini, xen-devel
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 <van.freenix@gmail.com>
>>> Cc: Stefano Stabellini <sstabellini@kernel.org>
>>> Cc: Julien Grall <julien.grall@arm.com>
>>> ---
>>> 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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Xen-devel mailing list
Xen-devel@lists.xen.org
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-05-12 6:36 [PATCH] xen/arm: mm: fix nr_second calculation in setup_frametable_mappings Peng Fan
2016-05-12 10:48 ` Julien Grall
2016-05-12 11:30 ` Peng Fan
2016-05-12 12:07 ` Julien Grall
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