On Thu, Nov 11, 2021 at 4:30 PM Jane Chu <[email protected]> wrote: > > Just a quick update - > > I managed to test the 'NP' and 'UC' effect on a pmem dax file. > The result is, as expected, both setting 'NP' and 'UC' works > well in preventing the prefetcher from accessing the poisoned > pmem page. > > I injected back-to-back poisons to the 3rd block(512B) of > the 3rd page in my dax file. With 'NP', the 'mc_safe read' > stops after reading the 1st and 2nd pages, with 'UC', > the 'mc_safe read' was able to read [2 pages + 2 blocks] on > my test machine.
My expectation is that dax_direct_access() / dax_recovery_read() has installed a temporary UC alias for the pfn, or has temporarily flipped NP to UC. Outside of dax_recovery_read() the page will always be NP.
