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    SubjectRe: invalidate caches before going into suspend

    * Mark Langsdorf <mark.langsdorf@amd.com> wrote:

    > When a CPU core is shut down, all of its caches need to be flushed to
    > prevent stale data from causing errors if the core is resumed. Current
    > Linux suspend code performs an assignment after the flush, which can
    > add dirty data back to the cache. On some AMD platforms, additional
    > speculative reads have caused crashes on resume because of this dirty
    > data.
    >
    > Relocate the cache flush to be the very last thing done before
    > halting.

    nice catch! Applied to x86/urgent.

    I'm really curious: how did you find this bug? Did you see a CPU come up
    as !CPU_DEAD?

    > Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
    > Acked-by: Mark Borden <mark.borden@amd.com>
    > Acked-by: Michael Hohmuth <michael.hohmuth@amd.com>
    >
    > diff -r f3f819497a68 arch/x86/kernel/process_64.c
    > --- a/arch/x86/kernel/process_64.c Thu Aug 07 04:24:53 2008 -0500
    > +++ b/arch/x86/kernel/process_64.c Tue Aug 12 07:11:36 2008 -0500
    > @@ -93,11 +93,11 @@ static inline void play_dead(void)
    > static inline void play_dead(void)
    > {
    > idle_task_exit();
    > - wbinvd();
    > mb();
    > /* Ack it */
    > __get_cpu_var(cpu_state) = CPU_DEAD;
    >
    > + wbinvd();
    > local_irq_disable();
    > while (1)
    > halt();

    please send a patch for the 32-bit side too, it has the same bug.

    also, we might be safer if the wbinvd(), the CLI and the halt was in a
    single assembly sequence:

    if (cpu >= i486)
    asm ("cli; wbinvd; cli; 1: hlt; jmp 1b")
    else
    asm ("cli; 1: hlt; jmp 1b")

    to make sure the compiler doesnt ever insert something into this
    codepath? [ And note the double cli which would be further
    robustification - in theory we could get a spurious interrupt straight
    after the wbinvd. ] Hm?

    Ingo


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