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    Subject[PATCH 4.16 110/113] x86/microcode: Do not exit early from __reload_late()
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Borislav Petkov <bp@suse.de>

    commit 09e182d17e8891dd73baba961a0f5a82e9274c97 upstream.

    Vitezslav reported a case where the

    "Timeout during microcode update!"

    panic would hit. After a deeper look, it turned out that his .config had
    CONFIG_HOTPLUG_CPU disabled which practically made save_mc_for_early() a
    no-op.

    When that happened, the discovered microcode patch wasn't saved into the
    cache and the late loading path wouldn't find any.

    This, then, lead to early exit from __reload_late() and thus CPUs waiting
    until the timeout is reached, leading to the panic.

    In hindsight, that function should have been written so it does not return
    before the post-synchronization. Oh well, I know better now...

    Fixes: bb8c13d61a62 ("x86/microcode: Fix CPU synchronization routine")
    Reported-by: Vitezslav Samel <vitezslav@samel.cz>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Vitezslav Samel <vitezslav@samel.cz>
    Tested-by: Ashok Raj <ashok.raj@intel.com>
    Cc: stable@vger.kernel.org
    Link: http://lkml.kernel.org/r/20180418081140.GA2439@pc11.op.pod.cz
    Link: https://lkml.kernel.org/r/20180421081930.15741-2-bp@alien8.de
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/cpu/microcode/core.c | 6 ++----
    1 file changed, 2 insertions(+), 4 deletions(-)

    --- a/arch/x86/kernel/cpu/microcode/core.c
    +++ b/arch/x86/kernel/cpu/microcode/core.c
    @@ -564,14 +564,12 @@ static int __reload_late(void *info)
    apply_microcode_local(&err);
    spin_unlock(&update_lock);

    + /* siblings return UCODE_OK because their engine got updated already */
    if (err > UCODE_NFOUND) {
    pr_warn("Error reloading microcode on CPU %d\n", cpu);
    - return -1;
    - /* siblings return UCODE_OK because their engine got updated already */
    + ret = -1;
    } else if (err == UCODE_UPDATED || err == UCODE_OK) {
    ret = 1;
    - } else {
    - return ret;
    }

    /*

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