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From: Alistair Popple <apopple@nvidia.com>
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Subject: Re: [PATCH v3 5/8] mm: Device exclusive memory access
Date: Thu, 4 Mar 2021 16:20:52 +1100
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On Tuesday, 2 March 2021 11:41:52 PM AEDT Jason Gunthorpe wrote:
> > However try_to_protect() scans the PTEs again under the PTL so checking 
the 
> > mapping of interest actually gets replaced during the rmap walk seems like 
a 
> > reasonable solution. Thanks for the comments.
> 
> It does seem cleaner if you can manage it, the notifier will still be
> needd to program the HW though

Checking during the rmap walk wasn't hard but ultimately pointless. As you say 
a range notifier and lock is required to program the hardware, which requires 
checking the mappings with a mmu notifier sequence anyway.

 - Alistair