• Borislav Petkov's avatar
    x86/microcode/intel: Drop stashed AP patch pointer optimization · c26665ab
    Borislav Petkov authored
    This was meant to save us the scanning of the microcode containter in
    the initrd since the first AP had already done that but it can also hurt
    us:
    
    Imagine a single hyperthreaded CPU (Intel(R) Atom(TM) CPU N270, for
    example) which updates the microcode on the BSP but since the microcode
    engine is shared between the two threads, the update on CPU1 doesn't
    happen because it has already happened on CPU0 and we don't find a newer
    microcode revision on CPU1.
    
    Which doesn't set the intel_ucode_patch pointer and at initrd
    jettisoning time we don't save the microcode patch for later
    application.
    
    Now, when we suspend to RAM, the loaded microcode gets cleared so we
    need to reload but there's no patch saved in the cache.
    
    Removing the optimization fixes this issue and all is fine and dandy.
    
    Fixes: 06b8534c ("x86/microcode: Rework microcode loading")
    Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
    Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/20170120202955.4091-2-bp@alien8.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    c26665ab
intel.c 20.9 KB