• Scott Wood's avatar
    powerpc/e6500: TLB miss handler with hardware tablewalk support · 28efc35f
    Scott Wood authored
    There are a few things that make the existing hw tablewalk handlers
    unsuitable for e6500:
    
     - Indirect entries go in TLB1 (though the resulting direct entries go in
       TLB0).
    
     - It has threads, but no "tlbsrx." -- so we need a spinlock and
       a normal "tlbsx".  Because we need this lock, hardware tablewalk
       is mandatory on e6500 unless we want to add spinlock+tlbsx to
       the normal bolted TLB miss handler.
    
     - TLB1 has no HES (nor next-victim hint) so we need software round robin
       (TODO: integrate this round robin data with hugetlb/KVM)
    
     - The existing tablewalk handlers map half of a page table at a time,
       because IBM hardware has a fixed 1MiB indirect page size.  e6500
       has variable size indirect entries, with a minimum of 2MiB.
       So we can't do the half-page indirect mapping, and even if we
       could it would be less efficient than mapping the full page.
    
     - Like on e5500, the linear mapping is bolted, so we don't need the
       overhead of supporting nested tlb misses.
    
    Note that hardware tablewalk does not work in rev1 of e6500.
    We do not expect to support e6500 rev1 in mainline Linux.
    Signed-off-by: default avatarScott Wood <scottwood@freescale.com>
    Cc: Mihai Caraman <mihai.caraman@freescale.com>
    28efc35f
paca.c 6.23 KB