On Fri, Nov 20, 2020 at 02:35:52PM +0000, Will Deacon wrote: > pte_accessible() is used by ptep_clear_flush() to figure out whether TLB > invalidation is necessary when unmapping pages for reclaim. Although our > implementation is correct according to the architecture, returning true > only for valid, young ptes in the absence of racing page-table > modifications, this is in fact flawed due to lazy invalidation of old > ptes in ptep_clear_flush_young() where we elide the expensive DSB > instruction for completing the TLB invalidation. > > Rather than penalise the aging path, adjust pte_accessible() to return > true for any valid pte, even if the access flag is cleared. > > Cc: <[email protected]> > Fixes: 76c714be0e5e ("arm64: pgtable: implement pte_accessible()") > Reported-by: Yu Zhao <[email protected]> > Signed-off-by: Will Deacon <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
