On Mon, 2023-12-25 at 11:05 +0300, Kirill A. Shutemov wrote: > If the helper is defined, it is called instead of halt() to stop the CPU > at the end of stop_this_cpu() and on crash CPU shutdown. > > ACPI MADT will use it to hand over the CPU to BIOS in order to be able > to wake it up again after kexec. > > Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> > --- > > v5.1: > - Fix build for !SMP; > > --- > arch/x86/include/asm/smp.h | 1 + > arch/x86/kernel/process.c | 7 +++++++ > arch/x86/kernel/reboot.c | 12 ++++++++---- > 3 files changed, 16 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h > index 4fab2ed454f3..390d53fd34f9 100644 > --- a/arch/x86/include/asm/smp.h > +++ b/arch/x86/include/asm/smp.h > @@ -38,6 +38,7 @@ struct smp_ops { > int (*cpu_disable)(void); > void (*cpu_die)(unsigned int cpu); > void (*play_dead)(void); > + void (*stop_this_cpu)(void); > > void (*send_call_func_ipi)(const struct cpumask *mask); > void (*send_call_func_single_ipi)(int cpu); > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > index b6f4e8399fca..ea4c812c7bf3 100644 > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -835,6 +835,13 @@ void __noreturn stop_this_cpu(void *dummy) > */ > cpumask_clear_cpu(cpu, &cpus_stop_mask); > > +#ifdef CONFIG_SMP > + if (smp_ops.stop_this_cpu) { > + smp_ops.stop_this_cpu(); > + unreachable(); > + } > +#endif
If I read correctly this will result in stop_this_cpu() having different behaviour for SMP and !SMP build for TDX guest. For example, AFAICT machine_halt() also calls stop_this_cpu() on local cpu after it stops other cpus. So for the local cpu, in SMP build it will calls into BIOS's reset vector but in !SMP it will call native_halt(). > + > for (;;) { > /* > * Use native_halt() so that memory contents don't change > diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c > index 16dde83df49a..738b3e810196 100644 > --- a/arch/x86/kernel/reboot.c > +++ b/arch/x86/kernel/reboot.c > @@ -881,10 +881,14 @@ static int crash_nmi_callback(unsigned int val, struct > pt_regs *regs) > cpu_emergency_disable_virtualization(); > > atomic_dec(&waiting_for_crash_ipi); > - /* Assume hlt works */ > - halt(); > - for (;;) > - cpu_relax(); > + > + if (smp_ops.stop_this_cpu) { > + smp_ops.stop_this_cpu(); Could you explain why unreachable() is called in stop_this_cpu() but not here? > + } else { > + halt(); > + for (;;) > + cpu_relax(); > + } Similar to stop_this_cpu(), if you also call unreachable() here, then I think you can remove the 'else' here but directly calls halt() + cpu_relax() loop. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec