From: Hidehiro Kawai <hidehiro.kawai.ez@xxxxxxxxxxx> Subject: x86/panic: replace smp_send_stop() with kdump friendly version in panic path Daniel Walker reported problems which happens when crash_kexec_post_notifiers kernel option is enabled (https://lkml.org/lkml/2015/6/24/44). In that case, smp_send_stop() is called before entering kdump routines which assume other CPUs are still online. As the result, for x86, kdump routines fail to save other CPUs' registers and disable virtualization extensions. To fix this problem, call a new kdump friendly function, crash_smp_send_stop(), instead of the smp_send_stop() when crash_kexec_post_notifiers is enabled. crash_smp_send_stop() is a weak function, and it just call smp_send_stop(). Architecture codes should override it so that kdump can work appropriately. This patch only provides x86-specific version. For Xen's PV kernel, just keep the current behavior. NOTES: - Right solution would be to place crash_smp_send_stop() before __crash_kexec() invocation in all cases and remove smp_send_stop(), but we can't do that until all architectures implement own crash_smp_send_stop() - crash_smp_send_stop()-like work is still needed by machine_crash_shutdown() because crash_kexec() can be called without entering panic() Fixes: f06e5153f4ae (kernel/panic.c: add "crash_kexec_post_notifiers" option) Link: http://lkml.kernel.org/r/20160810080948.11028.15344.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@xxxxxxxxxxx> Reported-by: Daniel Walker <dwalker@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Daniel Walker <dwalker@xxxxxxxxxx> Cc: Xunlei Pang <xpang@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: David Vrabel <david.vrabel@xxxxxxxxxx> Cc: Toshi Kani <toshi.kani@xxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: David Daney <david.daney@xxxxxxxxxx> Cc: Aaro Koskinen <aaro.koskinen@xxxxxx> Cc: "Steven J. Hill" <steven.hill@xxxxxxxxxx> Cc: Corey Minyard <cminyard@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/kexec.h | 1 arch/x86/include/asm/smp.h | 1 arch/x86/kernel/crash.c | 22 +++++++++++++-- arch/x86/kernel/smp.c | 5 +++ kernel/panic.c | 47 ++++++++++++++++++++++++++++----- 5 files changed, 66 insertions(+), 10 deletions(-) diff -puN arch/x86/include/asm/kexec.h~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path arch/x86/include/asm/kexec.h --- a/arch/x86/include/asm/kexec.h~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path +++ a/arch/x86/include/asm/kexec.h @@ -210,6 +210,7 @@ struct kexec_entry64_regs { typedef void crash_vmclear_fn(void); extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; +extern void kdump_nmi_shootdown_cpus(void); #endif /* __ASSEMBLY__ */ diff -puN arch/x86/include/asm/smp.h~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path arch/x86/include/asm/smp.h --- a/arch/x86/include/asm/smp.h~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path +++ a/arch/x86/include/asm/smp.h @@ -47,6 +47,7 @@ struct smp_ops { void (*smp_cpus_done)(unsigned max_cpus); void (*stop_other_cpus)(int wait); + void (*crash_stop_other_cpus)(void); void (*smp_send_reschedule)(int cpu); int (*cpu_up)(unsigned cpu, struct task_struct *tidle); diff -puN arch/x86/kernel/crash.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path arch/x86/kernel/crash.c --- a/arch/x86/kernel/crash.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path +++ a/arch/x86/kernel/crash.c @@ -133,15 +133,31 @@ static void kdump_nmi_callback(int cpu, disable_local_APIC(); } -static void kdump_nmi_shootdown_cpus(void) +void kdump_nmi_shootdown_cpus(void) { nmi_shootdown_cpus(kdump_nmi_callback); disable_local_APIC(); } +/* Override the weak function in kernel/panic.c */ +void crash_smp_send_stop(void) +{ + static int cpus_stopped; + + if (cpus_stopped) + return; + + if (smp_ops.crash_stop_other_cpus) + smp_ops.crash_stop_other_cpus(); + else + smp_send_stop(); + + cpus_stopped = 1; +} + #else -static void kdump_nmi_shootdown_cpus(void) +void crash_smp_send_stop(void) { /* There are no cpus to shootdown */ } @@ -160,7 +176,7 @@ void native_machine_crash_shutdown(struc /* The kernel is broken so disable interrupts */ local_irq_disable(); - kdump_nmi_shootdown_cpus(); + crash_smp_send_stop(); /* * VMCLEAR VMCSs loaded on this cpu if needed. diff -puN arch/x86/kernel/smp.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path arch/x86/kernel/smp.c --- a/arch/x86/kernel/smp.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path +++ a/arch/x86/kernel/smp.c @@ -32,6 +32,8 @@ #include <asm/nmi.h> #include <asm/mce.h> #include <asm/trace/irq_vectors.h> +#include <asm/kexec.h> + /* * Some notes on x86 processor bugs affecting SMP operation: * @@ -342,6 +344,9 @@ struct smp_ops smp_ops = { .smp_cpus_done = native_smp_cpus_done, .stop_other_cpus = native_stop_other_cpus, +#if defined(CONFIG_KEXEC_CORE) + .crash_stop_other_cpus = kdump_nmi_shootdown_cpus, +#endif .smp_send_reschedule = native_smp_send_reschedule, .cpu_up = native_cpu_up, diff -puN kernel/panic.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path kernel/panic.c --- a/kernel/panic.c~x86-panic-replace-smp_send_stop-with-kdump-friendly-version-in-panic-path +++ a/kernel/panic.c @@ -71,6 +71,32 @@ void __weak nmi_panic_self_stop(struct p panic_smp_self_stop(); } +/* + * Stop other CPUs in panic. Architecture dependent code may override this + * with more suitable version. For example, if the architecture supports + * crash dump, it should save registers of each stopped CPU and disable + * per-CPU features such as virtualization extensions. + */ +void __weak crash_smp_send_stop(void) +{ + static int cpus_stopped; + + /* + * This function can be called twice in panic path, but obviously + * we execute this only once. + */ + if (cpus_stopped) + return; + + /* + * Note smp_send_stop is the usual smp shutdown function, which + * unfortunately means it may not be hardened to work in a panic + * situation. + */ + smp_send_stop(); + cpus_stopped = 1; +} + atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID); /* @@ -164,14 +190,21 @@ void panic(const char *fmt, ...) if (!_crash_kexec_post_notifiers) { printk_nmi_flush_on_panic(); __crash_kexec(NULL); - } - /* - * Note smp_send_stop is the usual smp shutdown function, which - * unfortunately means it may not be hardened to work in a panic - * situation. - */ - smp_send_stop(); + /* + * Note smp_send_stop is the usual smp shutdown function, which + * unfortunately means it may not be hardened to work in a + * panic situation. + */ + smp_send_stop(); + } else { + /* + * If we want to do crash dump after notifier calls and + * kmsg_dump, we will need architecture dependent extra + * works in addition to stopping other CPUs. + */ + crash_smp_send_stop(); + } /* * Run any panic handlers, including those that might need to _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
