Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Philippe Gerum wrote:
>>> Jan Kiszka wrote:
>>>> Philippe Gerum wrote:
>>>>> Jan Kiszka wrote:
>>>>>> Philippe Gerum wrote:
>>>>>>> Jan Kiszka wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> doesn't this patch [1] have some relevance for us as well? As we use
>>>>>>>> xnarch_remap_io_page_range also for non-IO memory, I'm hesitating to
>>>>>>>> suggest that we apply this unconditionally at xnarch level. Ideas welcome.
>>>>>>>>
>>>>>>> Yes, I think it makes a lot of sense on powerpc at least, since doing so will
>>>>>>> set the PAGE_GUARDED bit as well, and we obviously want to avoid any
>>>>>>> out-of-order access of I/O memory.
>>>>>>>
>>>>>>> (I don't see the reason to force the VM_RESERVED and VM_IO on the vma though,
>>>>>>> since remap_pfn_range will do it anyway.)
>>>>>> No, I was talking about cases where we may pass kmalloc'ed memory to
>>>>>> xnarch_remap_io_page_range. In that case, caching and out-of-order
>>>>>> access may be desired for performance reasons.
>>>>>>
>>>>> xnarch_remap_io_page_range is intended for I/O memory only, some assumptions are
>>>>> made on this. rtdm_mmap_buffer() should be fixed; it would be much better to
>>>>> define another internal interface at xnarch level to specifically perform
>>>>> kmalloc mapping.
>>>> Yeah, probably. But I think the issue is not just limited to RTDM. The
>>>> xnheap can be kmalloc-hosted as well.
>>>>
>>> This one is used with DMA memory. What I would suggest, is something like this:
>>>
>>> --- ksrc/skins/rtdm/drvlib.c	(revision 3590)
>>> +++ ksrc/skins/rtdm/drvlib.c	(working copy)
>>> @@ -1738,9 +1738,12 @@
>>>  		}
>>>  		return 0;
>>>  	} else
>>> -#endif /* CONFIG_MMU */
>>>  		return xnarch_remap_io_page_range(vma, maddr, paddr,
>>>  						  size, PAGE_SHARED);
>>> +#else
>>> +	return xnarch_remap_kmem_page_range(vma, maddr, paddr,
>>> +					    size, PAGE_SHARED);
>>> +#endif /* CONFIG_MMU */
>>>  }
>>>
>>>  static struct file_operations rtdm_mmap_fops = {
>>>
>>>
>>> I.e. split the cases where MMU is absent from the one where MMU is there but we
>>> come from rtdm_iomap_to_user.
>> Makes no sense to me yet. With CONFIG_MMU we have 3 cases, not just two,
>> no? We have to use mmap_data->src_paddr to tell kmem_page apart from
>> io_page.
> 
> That's what the patch I sent right after this one does.

Nope, vaddr can be NULL in both cases, only paddr is differentiating.

This one should do what we need:

Index: ksrc/skins/rtdm/drvlib.c
===================================================================
--- ksrc/skins/rtdm/drvlib.c	(Revision 3594)
+++ ksrc/skins/rtdm/drvlib.c	(Arbeitskopie)
@@ -1739,8 +1739,12 @@ static int rtdm_mmap_buffer(struct file 
 		return 0;
 	} else
 #endif /* CONFIG_MMU */
+	if (mmap_data->src_paddr)
 		return xnarch_remap_io_page_range(vma, maddr, paddr,
 						  size, PAGE_SHARED);
+	else
+		return xnarch_remap_kmem_page_range(vma, maddr, paddr,
+						    size, PAGE_SHARED);
 }
 
 static struct file_operations rtdm_mmap_fops = {