| Message ID | 20230830121115.v12.6.I2ef26d1b3bfbed2d10a281942b0da7d9854de05e@changeid (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Add IPI for backtraces / kgdb; try to use NMI for some IPIs | expand |
On Wed, Aug 30, 2023 at 12:11:27PM -0700, Douglas Anderson wrote: > Up until now we've been using the generic (weak) implementation for > kgdb_roundup_cpus() when using kgdb on arm64. Let's move to a custom > one. The advantage here is that, when pseudo-NMI is enabled on a > device, we'll be able to round up CPUs using pseudo-NMI. This allows > us to debug CPUs that are stuck with interrupts disabled. If > pseudo-NMIs are not enabled then we'll fallback to just using an IPI, > which is still slightly better than the generic implementation since > it avoids the potential situation described in the generic > kgdb_call_nmi_hook(). > > Co-developed-by: Sumit Garg <sumit.garg@linaro.org> > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> > Reviewed-by: Stephen Boyd <swboyd@chromium.org> > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- > I debated whether this should be in "arch/arm64/kernel/smp.c" or if I > should try to find a way for it to go into "arch/arm64/kernel/kgdb.c". > In the end this is so little code that it didn't seem worth it to find > a way to export the IPI defines or to otherwise come up with some API > between kgdb.c and smp.c. If someone has strong feelings and wants > this to change, please shout and give details of your preferred > solution. Putting this in smp.c seems fine to me. Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > > FWIW, it seems like ~half the other platforms put this in "smp.c" with > an ifdef for KGDB and the other half put it in "kgdb.c" with an ifdef > for SMP. :-P > > (no changes since v10) > > Changes in v10: > - Don't allocate the cpumask on the stack; just iterate. > - Moved kgdb calls to smp.c to avoid needing to export IPI info. > - kgdb now has its own IPI. > > Changes in v9: > - Remove fallback for when debug IPI isn't available. > - Renamed "NMI IPI" to "debug IPI" since it might not be backed by NMI. > > arch/arm64/kernel/smp.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 800c59cf9b64..1a53e57c81d0 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -32,6 +32,7 @@ > #include <linux/irq_work.h> > #include <linux/kernel_stat.h> > #include <linux/kexec.h> > +#include <linux/kgdb.h> > #include <linux/kvm_host.h> > #include <linux/nmi.h> > > @@ -79,6 +80,7 @@ enum ipi_msg_type { > * with trace_ipi_* > */ > IPI_CPU_BACKTRACE = NR_IPI, > + IPI_KGDB_ROUNDUP, > MAX_IPI > }; > > @@ -868,6 +870,22 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > nmi_trigger_cpumask_backtrace(mask, exclude_cpu, arm64_backtrace_ipi); > } > > +#ifdef CONFIG_KGDB > +void kgdb_roundup_cpus(void) > +{ > + int this_cpu = raw_smp_processor_id(); > + int cpu; > + > + for_each_online_cpu(cpu) { > + /* No need to roundup ourselves */ > + if (cpu == this_cpu) > + continue; > + > + __ipi_send_single(ipi_desc[IPI_KGDB_ROUNDUP], cpu); > + } > +} > +#endif > + > /* > * Main handler for inter-processor interrupts > */ > @@ -919,6 +937,10 @@ static void do_handle_IPI(int ipinr) > nmi_cpu_backtrace(get_irq_regs()); > break; > > + case IPI_KGDB_ROUNDUP: > + kgdb_nmicallback(cpu, get_irq_regs()); > + break; > + > default: > pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr); > break; > @@ -949,6 +971,7 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi) > case IPI_CPU_STOP: > case IPI_CPU_CRASH_STOP: > case IPI_CPU_BACKTRACE: > + case IPI_KGDB_ROUNDUP: > return true; > default: > return false; > -- > 2.42.0.283.g2d96d420d3-goog >
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 800c59cf9b64..1a53e57c81d0 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -32,6 +32,7 @@ #include <linux/irq_work.h> #include <linux/kernel_stat.h> #include <linux/kexec.h> +#include <linux/kgdb.h> #include <linux/kvm_host.h> #include <linux/nmi.h> @@ -79,6 +80,7 @@ enum ipi_msg_type { * with trace_ipi_* */ IPI_CPU_BACKTRACE = NR_IPI, + IPI_KGDB_ROUNDUP, MAX_IPI }; @@ -868,6 +870,22 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) nmi_trigger_cpumask_backtrace(mask, exclude_cpu, arm64_backtrace_ipi); } +#ifdef CONFIG_KGDB +void kgdb_roundup_cpus(void) +{ + int this_cpu = raw_smp_processor_id(); + int cpu; + + for_each_online_cpu(cpu) { + /* No need to roundup ourselves */ + if (cpu == this_cpu) + continue; + + __ipi_send_single(ipi_desc[IPI_KGDB_ROUNDUP], cpu); + } +} +#endif + /* * Main handler for inter-processor interrupts */ @@ -919,6 +937,10 @@ static void do_handle_IPI(int ipinr) nmi_cpu_backtrace(get_irq_regs()); break; + case IPI_KGDB_ROUNDUP: + kgdb_nmicallback(cpu, get_irq_regs()); + break; + default: pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr); break; @@ -949,6 +971,7 @@ static bool ipi_should_be_nmi(enum ipi_msg_type ipi) case IPI_CPU_STOP: case IPI_CPU_CRASH_STOP: case IPI_CPU_BACKTRACE: + case IPI_KGDB_ROUNDUP: return true; default: return false;