• David S. Miller's avatar
    [SPARC64]: Fix boot failures on SunBlade-150 · c9c10830
    David S. Miller authored
    The sequence to move over to the Linux trap tables from
    the firmware ones needs to be more air tight.  It turns
    out that to be %100 safe we do need to be able to translate
    OBP mappings in our TLB miss handlers early.
    
    In order not to eat up a lot of kernel image memory with
    static page tables, just use the translations array in
    the OBP TLB miss handlers.  That solves the bulk of the
    problem.
    
    Furthermore, to make sure the OBP TLB miss path will work
    even before the fixed MMU globals are loaded, explicitly
    load %g1 to TLB_SFSR at the beginning of the i-TLB and
    d-TLB miss handlers.
    
    To ease the OBP TLB miss walking of the prom_trans[] array,
    we sort it then delete all of the non-OBP entries in there
    (for example, there are entries for the kernel image itself
    which we're not interested in at all).
    
    We also save about 32K of kernel image size with this change.
    Not a bad side effect :-)
    
    There are still some reasons why trampoline.S can't use the
    setup_trap_table() yet.  The most noteworthy are:
    
    1) OBP boots secondary processors with non-bias'd stack for
       some reason.  This is easily fixed by using a small bootup
       stack in the kernel image explicitly for this purpose.
    
    2) Doing a firmware call via the normal C call prom_set_trap_table()
       goes through the whole OBP enter/exit sequence that saves and
       restores OBP and Linux kernel state in the MMUs.  This path
       unfortunately does a "flush %g6" while loading up the OBP locked
       TLB entries for the firmware call.
    
       If we setup the %g6 in the trampoline.S code properly, that
       is in the PAGE_OFFSET linear mapping, but we're not on the
       kernel trap table yet so those addresses won't translate properly.
    
       One idea is to do a by-hand firmware call like we do in the
       early bootup code and elsewhere here in trampoline.S  But this
       fails as well, as aparently the secondary processors are not
       booted with OBP's special locked TLB entries loaded.  These
       are necessary for the firwmare to processes TLB misses correctly
       up until the point where we take over the trap table.
    
    This does need to be resolved at some point.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    c9c10830
itlb_base.S 2.44 KB