On Fri, 9 Oct 2020 14:59:52 -0700 Ralph Campbell rcampbell@nvidia.com wrote:
The code in mc_handle_swap_pte() checks for non_swap_entry() and returns NULL before checking is_device_private_entry() so device private pages are never handled. Fix this by checking for non_swap_entry() after handling device private swap PTEs.
Cc: stable@vger.kernel.org
I was going to ask "what are the end-user visible effects of the bug". This is important information with a cc:stable.
I'm not sure exactly how to test this. I ran the HMM self tests but that is a minimal sanity check. I think moving the self test from one memory cgroup to another while it is running would exercise this patch. I'm looking at how the test could move itself to another group after migrating some anonymous memory to the test driver.
But this makes me suspect the answer is "there aren't any that we know of". Are you sure a cc:stable is warranted?