Re: [Xenomai] rtdm_iomap_to_user: fix caching and page fault issues

[Wolfgang Grandegger <wg@grandegger.com>]

On 01/15/2013 08:46 PM, Gilles Chanteperdrix wrote:
> On 01/15/2013 04:22 PM, Wolfgang Grandegger wrote:
> 
>> From: Wolfgang Grandegger <wg@denx.de>
>>
>> Pages mapped by rtdm_iomap_to_user() might be cached and may
>> page fault on the first write. At least that's the behaviour
>> we observed on an ARM mx6q system. This patch fixes these
>> issues.
>>
>> Signed-off-by: Wolfgang Grandegger <wg@denx.de>
>> ---
>>  include/asm-generic/wrappers.h | 2 +-
>>  ksrc/skins/rtdm/drvlib.c       | 8 +++++---
>>  2 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/asm-generic/wrappers.h b/include/asm-generic/wrappers.h
>> index de1f0d7..e71bcc3 100644
>> --- a/include/asm-generic/wrappers.h
>> +++ b/include/asm-generic/wrappers.h
>> @@ -394,7 +394,7 @@ static inline void *kzalloc(size_t size, int flags)
>>  #define wrap_remap_io_page_range(vma,from,to,size,prot)  ({		\
>>      (vma)->vm_page_prot = pgprot_noncached((vma)->vm_page_prot);	\

Hm, here pgprot_noncached() is already used.

>>      /* Sets VM_RESERVED | VM_IO | VM_PFNMAP on the vma. */		\
>> -    remap_pfn_range(vma,from,(to) >> PAGE_SHIFT,size,prot);		\
>> +    remap_pfn_range(vma,from,(to) >> PAGE_SHIFT,size,pgprot_noncached(prot));		\
> 
> 
> Should not this be decided in the upper layers?

Upper layers? You mean calling xnarch_remap_io_page_range() with the
protection argument "pgprot_noncached(PAGE_SHARED)" in rtdm_mmap_buffer()?

Wolfgang.



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