Re: [Suspected SPAM] Re: [RFC PATCH 2/4] uverbs: Add common ib_iomem_get service

[Tom Tucker <tom-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 7/29/10 5:57 PM, Jason Gunthorpe wrote:
>> You would need to modify ib_umem_get() to check for the VM_PFNMAP
>> flag and build the struct ib_umem similar to the proposed
>> ib_iomem_get(). However, the page reference counting/sharing issue
>> would need to be solved. I think there are kernel level callbacks
>> for this that could be used.
>>      
> But in this case the pages are already mmaped into a user process,
> there must be some mechanism to ensure they don't get pulled away?!
>
>    
This is not virtual memory. It's real memory.

> Though, I guess, what happens if you hot un-plug the PCI-E card that
> has a process mmaping its memory?!
>
>    
Exactly. The memory would have to be physically detached for it to get 
'pulled away'

> What happens if you RDMA READ from PCI-E address space that does not
> have any device responding?
>
>    

bus error.

> Jason
>    

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