• Paul Mackerras's avatar
    powerpc: Make it possible to move the interrupt handlers away from the kernel · 1f6a93e4
    Paul Mackerras authored
    This changes the way that the exception prologs transfer control to
    the handlers in 64-bit kernels with the aim of making it possible to
    have the prologs separate from the main body of the kernel.  Now,
    instead of computing the address of the handler by taking the top
    32 bits of the paca address (to get the 0xc0000000........ part) and
    ORing in something in the bottom 16 bits, we get the base address of
    the kernel by doing a load from the paca and add an offset.
    
    This also replaces an mfmsr and an ori to compute the MSR value for
    the handler with a load from the paca.  That makes it unnecessary to
    have a separate version of EXCEPTION_PROLOG_PSERIES that forces 64-bit
    mode.
    
    We can no longer use a direct branches in the exception prolog code,
    which means that the SLB miss handlers can't branch directly to
    .slb_miss_realmode any more.  Instead we have to compute the address
    and do an indirect branch.  This is conditional on CONFIG_RELOCATABLE;
    for non-relocatable kernels we use a direct branch as before.  (A later
    change will allow CONFIG_RELOCATABLE to be set on 64-bit powerpc.)
    
    Since the secondary CPUs on pSeries start execution in the first 0x100
    bytes of real memory and then have to get to wherever the kernel is,
    we can't use a direct branch to get there.  Instead this changes
    __secondary_hold_spinloop from a flag to a function pointer.  When it
    is set to a non-NULL value, the secondary CPUs jump to the function
    pointed to by that value.
    
    Finally this eliminates one code difference between 32-bit and 64-bit
    by making __secondary_hold be the text address of the secondary CPU
    spinloop rather than a function descriptor for it.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    1f6a93e4
setup_64.c 15.5 KB