On Fri, Apr 24, 2020 at 06:11:35PM +0100, Will Deacon wrote: > My apologies, you're completely right. I thought that PAE mandated 64-bit > atomicity, like it does on 32-bit ARM, but that's apparently not the case > and looking at the 32-bit x86 pgtable code they have to be really careful > there. They added CMPXCHG8B for PAE, but then we never used it for that because it's dead slow (MS did use it I think). Instead we play horrible split word games, grep for CONFIG_GUP_GET_PTE_LOW_HIGH.
