• Arnd Bergmann's avatar
    powerpc/cell/axon-msi: Fix MSI after kexec · 23e0e8af
    Arnd Bergmann authored
    Commit d015fe99
    
     'powerpc/cell/axon-msi: Retry on missing interrupt'
    has turned a rare failure to kexec on QS22 into a reproducible
    error, which we have now analysed.
    
    The problem is that after a kexec, the MSIC hardware still points
    into the middle of the old ring buffer.  We set up the ring buffer
    during reboot, but not the offset into it.  On older kernels, this
    would cause a storm of thousands of spurious interrupts after a
    kexec, which would most of the time get dropped silently.
    
    With the new code, we time out on each interrupt, waiting for
    it to become valid.  If more interrupts come in that we time
    out on, this goes on indefinitely, which eventually leads to
    a hard crash.
    
    The solution in this commit is to read the current offset from
    the MSIC when reinitializing it.  This now works correctly, as
    expected.
    Reported-by: default avatarDirk Herrendoerfer <d.herrendoerfer@de.ibm.com>
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
    Acked-by: default avatarMichael Ellerman <michael@ellerman.id.au>
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    23e0e8af
axon_msi.c 11.5 KB