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    Subject[PATCH AUTOSEL 5.4 16/21] powerpc: handle kdump appropriately with crash_kexec_post_notifiers option
    Date
    From: Hari Bathini <hbathini@linux.ibm.com>

    [ Upstream commit 219572d2fc4135b5ce65c735d881787d48b10e71 ]

    Kdump can be triggered after panic_notifers since commit f06e5153f4ae2
    ("kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump
    after panic_notifers") introduced crash_kexec_post_notifiers option.
    But using this option would mean smp_send_stop(), that marks all other
    CPUs as offline, gets called before kdump is triggered. As a result,
    kdump routines fail to save other CPUs' registers. To fix this, kdump
    friendly crash_smp_send_stop() function was introduced with kernel
    commit 0ee59413c967 ("x86/panic: replace smp_send_stop() with kdump
    friendly version in panic path"). Override this kdump friendly weak
    function to handle crash_kexec_post_notifiers option appropriately
    on powerpc.

    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
    [Fixed signature of crash_stop_this_cpu() - reported by lkp@intel.com]
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20211207103719.91117-1-hbathini@linux.ibm.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/smp.c | 30 ++++++++++++++++++++++++++++++
    1 file changed, 30 insertions(+)

    diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
    index 82dff003a7fd6..4de63ec2e1551 100644
    --- a/arch/powerpc/kernel/smp.c
    +++ b/arch/powerpc/kernel/smp.c
    @@ -582,6 +582,36 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
    }
    #endif

    +#ifdef CONFIG_NMI_IPI
    +static void crash_stop_this_cpu(struct pt_regs *regs)
    +#else
    +static void crash_stop_this_cpu(void *dummy)
    +#endif
    +{
    + /*
    + * Just busy wait here and avoid marking CPU as offline to ensure
    + * register data is captured appropriately.
    + */
    + while (1)
    + cpu_relax();
    +}
    +
    +void crash_smp_send_stop(void)
    +{
    + static bool stopped = false;
    +
    + if (stopped)
    + return;
    +
    + stopped = true;
    +
    +#ifdef CONFIG_NMI_IPI
    + smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, crash_stop_this_cpu, 1000000);
    +#else
    + smp_call_function(crash_stop_this_cpu, NULL, 0);
    +#endif /* CONFIG_NMI_IPI */
    +}
    +
    #ifdef CONFIG_NMI_IPI
    static void nmi_stop_this_cpu(struct pt_regs *regs)
    {
    --
    2.34.1
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