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. Changes in V4: - Keep to use smp_send_stop if crash_kexec_post_notifiers is not set - Rename panic_smp_send_stop to crash_smp_send_stop - Don't change the behavior for Xen's PV kernel Changes in V3: - Revise comments, description, and symbol names Changes in V2: - Replace smp_send_stop() call with crash_kexec version which saves cpu states and cleans up VMX/SVM - Drop a fix for Problem 1 at this moment Reported-by: Daniel Walker <dwalker at fifo99.com> Fixes: f06e5153f4ae (kernel/panic.c: add "crash_kexec_post_notifiers" option) Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez at hitachi.com> Cc: Dave Young <dyoung at redhat.com> Cc: Baoquan He <bhe at redhat.com> Cc: Vivek Goyal <vgoyal at redhat.com> Cc: Eric Biederman <ebiederm at xmission.com> Cc: Masami Hiramatsu <mhiramat at kernel.org> Cc: Daniel Walker <dwalker at fifo99.com> Cc: Xunlei Pang <xpang at redhat.com> Cc: Thomas Gleixner <tglx at linutronix.de> Cc: Ingo Molnar <mingo at redhat.com> Cc: "H. Peter Anvin" <hpa at zytor.com> Cc: Borislav Petkov <bp at suse.de> Cc: David Vrabel <david.vrabel at citrix.com> Cc: Toshi Kani <toshi.kani at hpe.com> Cc: Andrew Morton <akpm at linux-foundation.org> --- 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 --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h index d2434c1..282630e 100644 --- a/arch/x86/include/asm/kexec.h +++ b/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 --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index ebd0c16..f70989c 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -50,6 +50,7 @@ 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 --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 9616cf7..650830e 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -133,15 +133,31 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs) 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(struct pt_regs *regs) /* 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 --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 658777c..68f8cc2 100644 --- a/arch/x86/kernel/smp.c +++ b/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 --git a/kernel/panic.c b/kernel/panic.c index ca8cea1..e6480e2 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -71,6 +71,32 @@ void __weak nmi_panic_self_stop(struct pt_regs *regs) 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
