From: Douglas Anderson <dianders@chromium.org> To: Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Sumit Garg <sumit.garg@linaro.org>, Daniel Thompson <daniel.thompson@linaro.org>, Marc Zyngier <maz@kernel.org> Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>, linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, kgdb-bugreport@lists.sourceforge.net, ito-yuichi@fujitsu.com, Stephen Boyd <swboyd@chromium.org>, Thomas Gleixner <tglx@linutronix.de>, Chen-Yu Tsai <wens@csie.org>, Ard Biesheuvel <ardb@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Masayoshi Mizuma <msys.mizuma@gmail.com>, Douglas Anderson <dianders@chromium.org>, D Scott Phillips <scott@os.amperecomputing.com>, Josh Poimboeuf <jpoimboe@kernel.org>, Valentin Schneider <vschneid@redhat.com>, linux-kernel@vger.kernel.org Subject: [PATCH v10 6/6] arm64: kgdb: Implement kgdb_roundup_cpus() to enable pseudo-NMI roundup Date: Tue, 22 Aug 2023 14:27:01 -0700 [thread overview] Message-ID: <20230822142644.v10.6.I2ef26d1b3bfbed2d10a281942b0da7d9854de05e@changeid> (raw) In-Reply-To: <20230822212927.249645-1-dianders@chromium.org> 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> 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. 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 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 | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index c51d54019f5f..5ee6b69b4360 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> @@ -75,10 +76,11 @@ enum ipi_msg_type { IPI_IRQ_WORK, NR_IPI, /* - * CPU_BACKTRACE is special and not included in NR_IPI + * CPU_BACKTRACE and KGDB_ROUNDUP are special and not included in NR_IPI * or tracable 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.rc1.204.g551eb34607-goog
WARNING: multiple messages have this Message-ID (diff)
From: Douglas Anderson <dianders@chromium.org> To: Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Sumit Garg <sumit.garg@linaro.org>, Daniel Thompson <daniel.thompson@linaro.org>, Marc Zyngier <maz@kernel.org> Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>, linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, kgdb-bugreport@lists.sourceforge.net, ito-yuichi@fujitsu.com, Stephen Boyd <swboyd@chromium.org>, Thomas Gleixner <tglx@linutronix.de>, Chen-Yu Tsai <wens@csie.org>, Ard Biesheuvel <ardb@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Masayoshi Mizuma <msys.mizuma@gmail.com>, Douglas Anderson <dianders@chromium.org>, D Scott Phillips <scott@os.amperecomputing.com>, Josh Poimboeuf <jpoimboe@kernel.org>, Valentin Schneider <vschneid@redhat.com>, linux-kernel@vger.kernel.org Subject: [PATCH v10 6/6] arm64: kgdb: Implement kgdb_roundup_cpus() to enable pseudo-NMI roundup Date: Tue, 22 Aug 2023 14:27:01 -0700 [thread overview] Message-ID: <20230822142644.v10.6.I2ef26d1b3bfbed2d10a281942b0da7d9854de05e@changeid> (raw) In-Reply-To: <20230822212927.249645-1-dianders@chromium.org> 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> 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. 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 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 | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index c51d54019f5f..5ee6b69b4360 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> @@ -75,10 +76,11 @@ enum ipi_msg_type { IPI_IRQ_WORK, NR_IPI, /* - * CPU_BACKTRACE is special and not included in NR_IPI + * CPU_BACKTRACE and KGDB_ROUNDUP are special and not included in NR_IPI * or tracable 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.rc1.204.g551eb34607-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-08-22 21:31 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-22 21:26 [PATCH v10 0/6] arm64: Add IPI for backtraces / kgdb; try to use NMI for some IPIs Douglas Anderson 2023-08-22 21:26 ` Douglas Anderson 2023-08-22 21:26 ` [PATCH v10 1/6] irqchip/gic-v3: Enable support for SGIs to act as NMIs Douglas Anderson 2023-08-22 21:26 ` Douglas Anderson 2023-08-22 21:26 ` [PATCH v10 2/6] arm64: idle: Tag the arm64 idle functions as __cpuidle Douglas Anderson 2023-08-22 21:26 ` Douglas Anderson 2023-08-22 23:14 ` Stephen Boyd 2023-08-22 23:14 ` Stephen Boyd 2023-08-22 21:26 ` [PATCH v10 3/6] arm64: smp: Remove dedicated wakeup IPI Douglas Anderson 2023-08-22 21:26 ` Douglas Anderson 2023-08-22 23:16 ` Stephen Boyd 2023-08-22 23:16 ` Stephen Boyd 2023-08-22 21:26 ` [PATCH v10 4/6] arm64: smp: Add arch support for backtrace using pseudo-NMI Douglas Anderson 2023-08-22 21:26 ` Douglas Anderson 2023-08-22 23:39 ` Stephen Boyd 2023-08-22 23:39 ` Stephen Boyd 2023-08-23 19:58 ` kernel test robot 2023-08-23 19:58 ` kernel test robot 2023-08-22 21:27 ` [PATCH v10 5/6] arm64: smp: IPI_CPU_STOP and IPI_CPU_CRASH_STOP should try for NMI Douglas Anderson 2023-08-22 21:27 ` Douglas Anderson 2023-08-22 23:41 ` Stephen Boyd 2023-08-22 23:41 ` Stephen Boyd 2023-08-22 21:27 ` Douglas Anderson [this message] 2023-08-22 21:27 ` [PATCH v10 6/6] arm64: kgdb: Implement kgdb_roundup_cpus() to enable pseudo-NMI roundup Douglas Anderson 2023-08-22 23:50 ` Stephen Boyd 2023-08-22 23:50 ` Stephen Boyd
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