[PATCH 03/37] iommu/sva: Manage process address spaces

[Jean-Philippe Brucker]

On 24/04/18 18:17, Sinan Kaya wrote:
> On 4/24/2018 5:33 AM, Jean-Philippe Brucker wrote:
>>> Please return pasid when you find an io_mm that is already bound. Something like
>>> *pasid = io_mm->pasid should do the work here when bond is true.
>> Right. I think we should also keep returning 0, not switch to -EEXIST or
>> similar. So in next version a driver can call bind(devX, mmY) multiple
>> times, but the first unbind() removes the bond.
> 
> If we are going to allow multiple binds, then the last unbind should
> remove the bond rather than the first one via reference counting.

Yeah that's probably better. Since a bond belongs to a device driver it
doesn't need multiple bind/unbind, so earlier in this thread (1/37) I
talked about removing the bond->refs. But thinking about it, there still
is a need for it. When mm exits, we now need to call the device driver's
mm_exit handler outside of the spinlock, so we have to take a ref in
order to prevent a concurrent unbind() from freeing the bond.

Thanks,
Jean