• Nicholas Piggin's avatar
    powerpc/64s: Fix system reset vs general interrupt reentrancy · a3d96f70
    Nicholas Piggin authored
    The system reset interrupt can occur when MSR_EE=0, and it currently
    uses the PACA_EXGEN save area.
    
    Some PACA_EXGEN interrupts have a window where MSR_RI=1 and MSR_EE=0
    when the save area is still in use. A system reset interrupt in this
    window can lead to undetected corruption when the save area gets
    overwritten.
    
    This patch introduces PACA_EXNMI save area for system reset exceptions,
    which closes this corruption window. It's also helpful to retain the
    EXGEN state for debugging situations, even if not considering the
    recoverability aspect.
    
    This patch also moves the PACA_EXMC area down to a less frequently used
    part of the paca with the new save area.
    Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    a3d96f70
paca.h 7.21 KB