On Mon, Mar 7, 2016 at 9:46 AM, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote: > On 03/07/2016 08:06 AM, Khalid Aziz wrote: >> Top 4-bits of sparc64 virtual address are used for version tag only when >> a process has its PSTATE.mcde bit set and it is accessing a memory >> region that has ADI enabled on it (TTE.mcd set) and a version tag was >> set on the virtual address being accessed. These 4-bits retain their >> original semantics in all other cases. > > OK, so this effectively reduces the address space of a process using the > feature. Do we need to do anything explicit to keep an app from using > that address space? Do we make sure the kernel doesn't place VMAs > there? Do we respect mmap() hints that try to place memory there? Also, what happens when someone does this to an aliased page? This could be a MAP_SHARED mapping or a not-yet-COWed MAP_ANONYMOUS mapping. Also, what am I missing? Tying these tags to the physical page seems like a poor design to me. This seems really awkward to use. -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
