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arm64: smp: Add arch support for backtrace using pseudo-NMI

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Enable arch_trigger_cpumask_backtrace() support on arm64. This enables
things much like they are enabled on arm32 (including some of the
funky logic around NR_IPI, nr_ipi, and MAX_IPI) but with the
difference that, unlike arm32, we'll try to enable the backtrace to
use pseudo-NMI.

NOTE: this patch is a squash of the little bit of code adding the
ability to mark an IPI to try to use pseudo-NMI plus the little bit of
code to hook things up for kgdb. This approach was decided upon in the
discussion of v9 [1].

This patch depends on commit 8d539b84f1 ("nmi_backtrace: allow
excluding an arbitrary CPU") since that commit changed the prototype
of arch_trigger_cpumask_backtrace(), which this patch implements.

[1] https://lore.kernel.org/r/ZORY51mF4alI41G1@FVFF77S0Q05N

Co-developed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Co-developed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Misono Tomohiro <misono.tomohiro@fujitsu.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230906090246.v13.4.Ie6c132b96ebbbcddbf6954b9469ed40a6960343c@changeid
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Douglas Anderson 2023-09-06 09:02:59 -07:00 committed by Catalin Marinas
parent 2b2d0a7a96
commit 331a1b3a83
2 changed files with 78 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/arm64/include/asm/irq.h
View File

@ -6,6 +6,9 @@
#include <asm-generic/irq.h>
void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu);
#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
struct pt_regs;
int set_handle_irq(void (*handle_irq)(struct pt_regs *));

86
arch/arm64/kernel/smp.c
View File

@ -33,6 +33,7 @@
#include <linux/kernel_stat.h>
#include <linux/kexec.h>
#include <linux/kvm_host.h>
#include <linux/nmi.h>
#include <asm/alternative.h>
#include <asm/atomic.h>
@ -72,12 +73,18 @@ enum ipi_msg_type {
IPI_CPU_CRASH_STOP,
IPI_TIMER,
IPI_IRQ_WORK,
NR_IPI
NR_IPI,
/*
* Any enum >= NR_IPI and < MAX_IPI is special and not tracable
* with trace_ipi_*
*/
IPI_CPU_BACKTRACE = NR_IPI,
MAX_IPI
};
static int ipi_irq_base __read_mostly;
static int nr_ipi __read_mostly = NR_IPI;
static struct irq_desc *ipi_desc[NR_IPI] __read_mostly;
static struct irq_desc *ipi_desc[MAX_IPI] __read_mostly;
static void ipi_setup(int cpu);
@ -845,6 +852,22 @@ static void __noreturn ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs
#endif
}
static void arm64_backtrace_ipi(cpumask_t *mask)
{
__ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
}
void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
{
/*
* NOTE: though nmi_trigger_cpumask_backtrace() has "nmi_" in the name,
* nothing about it truly needs to be implemented using an NMI, it's
* just that it's _allowed_ to work with NMIs. If ipi_should_be_nmi()
* returned false our backtrace attempt will just use a regular IPI.
*/
nmi_trigger_cpumask_backtrace(mask, exclude_cpu, arm64_backtrace_ipi);
}
/*
* Main handler for inter-processor interrupts
*/
@ -888,6 +911,14 @@ static void do_handle_IPI(int ipinr)
break;
#endif
case IPI_CPU_BACKTRACE:
/*
* NOTE: in some cases this _won't_ be NMI context. See the
* comment in arch_trigger_cpumask_backtrace().
*/
nmi_cpu_backtrace(get_irq_regs());
break;
default:
pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
break;
@ -909,6 +940,19 @@ static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
__ipi_send_mask(ipi_desc[ipinr], target);
}
static bool ipi_should_be_nmi(enum ipi_msg_type ipi)
{
if (!system_uses_irq_prio_masking())
return false;
switch (ipi) {
case IPI_CPU_BACKTRACE:
return true;
default:
return false;
}
}
static void ipi_setup(int cpu)
{
int i;
@ -916,8 +960,14 @@ static void ipi_setup(int cpu)
if (WARN_ON_ONCE(!ipi_irq_base))
return;
for (i = 0; i < nr_ipi; i++)
enable_percpu_irq(ipi_irq_base + i, 0);
for (i = 0; i < nr_ipi; i++) {
if (ipi_should_be_nmi(i)) {
prepare_percpu_nmi(ipi_irq_base + i);
enable_percpu_nmi(ipi_irq_base + i, 0);
} else {
enable_percpu_irq(ipi_irq_base + i, 0);
}
}
}
#ifdef CONFIG_HOTPLUG_CPU
@ -928,8 +978,14 @@ static void ipi_teardown(int cpu)
if (WARN_ON_ONCE(!ipi_irq_base))
return;
for (i = 0; i < nr_ipi; i++)
disable_percpu_irq(ipi_irq_base + i);
for (i = 0; i < nr_ipi; i++) {
if (ipi_should_be_nmi(i)) {
disable_percpu_nmi(ipi_irq_base + i);
teardown_percpu_nmi(ipi_irq_base + i);
} else {
disable_percpu_irq(ipi_irq_base + i);
}
}
}
#endif
@ -937,15 +993,23 @@ void __init set_smp_ipi_range(int ipi_base, int n)
{
int i;
WARN_ON(n < NR_IPI);
nr_ipi = min(n, NR_IPI);
WARN_ON(n < MAX_IPI);
nr_ipi = min(n, MAX_IPI);
for (i = 0; i < nr_ipi; i++) {
int err;
err = request_percpu_irq(ipi_base + i, ipi_handler,
"IPI", &cpu_number);
WARN_ON(err);
if (ipi_should_be_nmi(i)) {
err = request_percpu_nmi(ipi_base + i, ipi_handler,
"IPI", &cpu_number);
WARN(err, "Could not request IPI %d as NMI, err=%d\n",
i, err);
} else {
err = request_percpu_irq(ipi_base + i, ipi_handler,
"IPI", &cpu_number);
WARN(err, "Could not request IPI %d as IRQ, err=%d\n",
i, err);
}
ipi_desc[i] = irq_to_desc(ipi_base + i);
irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);