They are held in the page tables and set in the hardware - in extra memory that is not software accessible except through a few supervisor-level instructions such as SSK (set storage key) - when the page is assigned to a real storage frame.
On Tue, Nov 22, 2022 at 10:24 AM Ian Worthington < [email protected]> wrote: > I don't think the storage keys (and their friends) are held in the page > tables though. > > > Best wishes / Mejores deseos / Meilleurs vœux > > Ian ... > > On Tuesday, November 22, 2022 at 05:04:08 PM GMT+1, Jay Maynard < > [email protected]> wrote: > > Each page table entry has a byte associated with it that stores the key, > as > well as the referenced and changed bits. > > And yes, 4K page tables do soak up lots of memory, which is why later OSes > use 1M or 2M pages. > > On Tue, Nov 22, 2022 at 9:22 AM Ian Worthington < > [email protected]> wrote: > > > Does anyone know where the storage protection keys are kept? It seems > > that the processors maintain recent keys in the TLB to be accessed by the > > DAT, but where do they live when they're not in the TLB? Surely we need > > one byte per 4k page per address space, which could be quite a bit of > > storage, so I'm assuming this has to be above the bar now? I can't see > any > > information in the pop about this. > > > > > > Best wishes / Mejores deseos / Meilleurs vœux > > > > Ian ... > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to [email protected] with the message: INFO IBM-MAIN > > > > > -- > Jay Maynard > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Jay Maynard ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
