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linux/arch/powerpc/kernel/irq.c
Michael Ellerman 4eb20bf34e powerpc/irq: Allow softirq to hardirq stack transition 
Allow a transition from the softirq stack to the hardirq stack when
handling a hardirq. Doing so means a hardirq received while deep in
softirq processing is less likely to cause a stack overflow of the
softirq stack.

Previously it wasn't safe to do so because irq_exit() (which initiates
softirq processing) was called on the hardirq stack.

That was changed in commit 1b1b6a6f4c ("powerpc: handle irq_enter/
irq_exit in interrupt handler wrappers") and 1346d00e1b ("powerpc:
Don't select HAVE_IRQ_EXIT_ON_IRQ_STACK").

The allowed transitions are now:
 - process stack -> hardirq stack
 - process stack -> softirq stack
 - process stack -> softirq stack -> hardirq stack

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231130125045.3080961-1-mpe@ellerman.id.au
2024-03-03 22:20:29 +11:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Derived from arch/i386/kernel/irq.c
* Copyright (C) 1992 Linus Torvalds
* Adapted from arch/i386 by Gary Thomas
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
* Updated and modified by Cort Dougan <cort@fsmlabs.com>
* Copyright (C) 1996-2001 Cort Dougan
* Adapted for Power Macintosh by Paul Mackerras
* Copyright (C) 1996 Paul Mackerras (paulus@cs.anu.edu.au)
*
* This file contains the code used by various IRQ handling routines:
* asking for different IRQ's should be done through these routines
* instead of just grabbing them. Thus setups with different IRQ numbers
* shouldn't result in any weird surprises, and installing new handlers
* should be easier.
*
* The MPC8xx has an interrupt mask in the SIU. If a bit is set, the
* interrupt is _enabled_. As expected, IRQ0 is bit 0 in the 32-bit
* mask register (of which only 16 are defined), hence the weird shifting
* and complement of the cached_irq_mask. I want to be able to stuff
* this right into the SIU SMASK register.
* Many of the prep/chrp functions are conditional compiled on CONFIG_PPC_8xx
* to reduce code space and undefined function references.
*/
#undef DEBUG
#include <linux/export.h>
#include <linux/threads.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/profile.h>
#include <linux/bitops.h>
#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/mutex.h>
#include <linux/pci.h>
#include <linux/debugfs.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/vmalloc.h>
#include <linux/pgtable.h>
#include <linux/static_call.h>
#include <linux/uaccess.h>
#include <asm/interrupt.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/cache.h>
#include <asm/ptrace.h>
#include <asm/machdep.h>
#include <asm/udbg.h>
#include <asm/smp.h>
#include <asm/hw_irq.h>
#include <asm/softirq_stack.h>
#include <asm/ppc_asm.h>
#define CREATE_TRACE_POINTS
#include <asm/trace.h>
#include <asm/cpu_has_feature.h>
DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
EXPORT_PER_CPU_SYMBOL(irq_stat);
#ifdef CONFIG_PPC32
atomic_t ppc_n_lost_interrupts;
#ifdef CONFIG_TAU_INT
extern int tau_initialized;
u32 tau_interrupts(unsigned long cpu);
#endif
#endif /* CONFIG_PPC32 */
int arch_show_interrupts(struct seq_file *p, int prec)
{
int j;
#if defined(CONFIG_PPC32) && defined(CONFIG_TAU_INT)
if (tau_initialized) {
seq_printf(p, "%*s: ", prec, "TAU");
for_each_online_cpu(j)
seq_printf(p, "%10u ", tau_interrupts(j));
seq_puts(p, " PowerPC Thermal Assist (cpu temp)\n");
}
#endif /* CONFIG_PPC32 && CONFIG_TAU_INT */
seq_printf(p, "%*s: ", prec, "LOC");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).timer_irqs_event);
seq_printf(p, " Local timer interrupts for timer event device\n");
seq_printf(p, "%*s: ", prec, "BCT");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).broadcast_irqs_event);
seq_printf(p, " Broadcast timer interrupts for timer event device\n");
seq_printf(p, "%*s: ", prec, "LOC");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).timer_irqs_others);
seq_printf(p, " Local timer interrupts for others\n");
seq_printf(p, "%*s: ", prec, "SPU");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).spurious_irqs);
seq_printf(p, " Spurious interrupts\n");
seq_printf(p, "%*s: ", prec, "PMI");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).pmu_irqs);
seq_printf(p, " Performance monitoring interrupts\n");
seq_printf(p, "%*s: ", prec, "MCE");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).mce_exceptions);
seq_printf(p, " Machine check exceptions\n");
#ifdef CONFIG_PPC_BOOK3S_64
if (cpu_has_feature(CPU_FTR_HVMODE)) {
seq_printf(p, "%*s: ", prec, "HMI");
for_each_online_cpu(j)
seq_printf(p, "%10u ", paca_ptrs[j]->hmi_irqs);
seq_printf(p, " Hypervisor Maintenance Interrupts\n");
}
#endif
seq_printf(p, "%*s: ", prec, "NMI");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).sreset_irqs);
seq_printf(p, " System Reset interrupts\n");
#ifdef CONFIG_PPC_WATCHDOG
seq_printf(p, "%*s: ", prec, "WDG");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).soft_nmi_irqs);
seq_printf(p, " Watchdog soft-NMI interrupts\n");
#endif
#ifdef CONFIG_PPC_DOORBELL
if (cpu_has_feature(CPU_FTR_DBELL)) {
seq_printf(p, "%*s: ", prec, "DBL");
for_each_online_cpu(j)
seq_printf(p, "%10u ", per_cpu(irq_stat, j).doorbell_irqs);
seq_printf(p, " Doorbell interrupts\n");
}
#endif
return 0;
}
/*
* /proc/stat helpers
*/
u64 arch_irq_stat_cpu(unsigned int cpu)
{
u64 sum = per_cpu(irq_stat, cpu).timer_irqs_event;
sum += per_cpu(irq_stat, cpu).broadcast_irqs_event;
sum += per_cpu(irq_stat, cpu).pmu_irqs;
sum += per_cpu(irq_stat, cpu).mce_exceptions;
sum += per_cpu(irq_stat, cpu).spurious_irqs;
sum += per_cpu(irq_stat, cpu).timer_irqs_others;
#ifdef CONFIG_PPC_BOOK3S_64
sum += paca_ptrs[cpu]->hmi_irqs;
#endif
sum += per_cpu(irq_stat, cpu).sreset_irqs;
#ifdef CONFIG_PPC_WATCHDOG
sum += per_cpu(irq_stat, cpu).soft_nmi_irqs;
#endif
#ifdef CONFIG_PPC_DOORBELL
sum += per_cpu(irq_stat, cpu).doorbell_irqs;
#endif
return sum;
}
static inline void check_stack_overflow(unsigned long sp)
{
if (!IS_ENABLED(CONFIG_DEBUG_STACKOVERFLOW))
return;
sp &= THREAD_SIZE - 1;
/* check for stack overflow: is there less than 1/4th free? */
if (unlikely(sp < THREAD_SIZE / 4)) {
pr_err("do_IRQ: stack overflow: %ld\n", sp);
dump_stack();
}
}
#ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
static __always_inline void call_do_softirq(const void *sp)
{
/* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
asm volatile (
PPC_STLU " %%r1, %[offset](%[sp]) ;"
"mr %%r1, %[sp] ;"
#ifdef CONFIG_PPC_KERNEL_PCREL
"bl %[callee]@notoc ;"
#else
"bl %[callee] ;"
#endif
PPC_LL " %%r1, 0(%%r1) ;"
: // Outputs
: // Inputs
[sp] "b" (sp), [offset] "i" (THREAD_SIZE - STACK_FRAME_MIN_SIZE),
[callee] "i" (__do_softirq)
: // Clobbers
"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
"cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
"r11", "r12"
);
}
#endif
DEFINE_STATIC_CALL_RET0(ppc_get_irq, *ppc_md.get_irq);
static void __do_irq(struct pt_regs *regs, unsigned long oldsp)
{
unsigned int irq;
trace_irq_entry(regs);
check_stack_overflow(oldsp);
/*
* Query the platform PIC for the interrupt & ack it.
*
* This will typically lower the interrupt line to the CPU
*/
irq = static_call(ppc_get_irq)();
/* We can hard enable interrupts now to allow perf interrupts */
if (should_hard_irq_enable(regs))
do_hard_irq_enable();
/* And finally process it */
if (unlikely(!irq))
__this_cpu_inc(irq_stat.spurious_irqs);
else
generic_handle_irq(irq);
trace_irq_exit(regs);
}
static __always_inline void call_do_irq(struct pt_regs *regs, void *sp)
{
register unsigned long r3 asm("r3") = (unsigned long)regs;
/* Temporarily switch r1 to sp, call __do_irq() then restore r1. */
asm volatile (
PPC_STLU " %%r1, %[offset](%[sp]) ;"
"mr %%r4, %%r1 ;"
"mr %%r1, %[sp] ;"
#ifdef CONFIG_PPC_KERNEL_PCREL
"bl %[callee]@notoc ;"
#else
"bl %[callee] ;"
#endif
PPC_LL " %%r1, 0(%%r1) ;"
: // Outputs
"+r" (r3)
: // Inputs
[sp] "b" (sp), [offset] "i" (THREAD_SIZE - STACK_FRAME_MIN_SIZE),
[callee] "i" (__do_irq)
: // Clobbers
"lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6",
"cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
"r11", "r12"
);
}
void __do_IRQ(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
void *cursp, *irqsp;
/* Switch to the irq stack to handle this */
cursp = (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
irqsp = hardirq_ctx[raw_smp_processor_id()];
/* Already there ? If not switch stack and call */
if (unlikely(cursp == irqsp))
__do_irq(regs, current_stack_pointer);
else
call_do_irq(regs, irqsp);
set_irq_regs(old_regs);
}
DEFINE_INTERRUPT_HANDLER_ASYNC(do_IRQ)
{
__do_IRQ(regs);
}
static void *__init alloc_vm_stack(void)
{
return __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, THREADINFO_GFP,
NUMA_NO_NODE, (void *)_RET_IP_);
}
static void __init vmap_irqstack_init(void)
{
int i;
for_each_possible_cpu(i) {
softirq_ctx[i] = alloc_vm_stack();
hardirq_ctx[i] = alloc_vm_stack();
}
}
void __init init_IRQ(void)
{
if (IS_ENABLED(CONFIG_VMAP_STACK))
vmap_irqstack_init();
if (ppc_md.init_IRQ)
ppc_md.init_IRQ();
if (!WARN_ON(!ppc_md.get_irq))
static_call_update(ppc_get_irq, ppc_md.get_irq);
}
#ifdef CONFIG_BOOKE_OR_40x
void *critirq_ctx[NR_CPUS] __read_mostly;
void *dbgirq_ctx[NR_CPUS] __read_mostly;
void *mcheckirq_ctx[NR_CPUS] __read_mostly;
#endif
void *softirq_ctx[NR_CPUS] __read_mostly;
void *hardirq_ctx[NR_CPUS] __read_mostly;
#ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
void do_softirq_own_stack(void)
{
call_do_softirq(softirq_ctx[smp_processor_id()]);
}
#endif
irq_hw_number_t virq_to_hw(unsigned int virq)
{
struct irq_data *irq_data = irq_get_irq_data(virq);
return WARN_ON(!irq_data) ? 0 : irq_data->hwirq;
}
EXPORT_SYMBOL_GPL(virq_to_hw);
#ifdef CONFIG_SMP
int irq_choose_cpu(const struct cpumask *mask)
{
int cpuid;
if (cpumask_equal(mask, cpu_online_mask)) {
static int irq_rover;
static DEFINE_RAW_SPINLOCK(irq_rover_lock);
unsigned long flags;
/* Round-robin distribution... */
do_round_robin:
raw_spin_lock_irqsave(&irq_rover_lock, flags);
irq_rover = cpumask_next(irq_rover, cpu_online_mask);
if (irq_rover >= nr_cpu_ids)
irq_rover = cpumask_first(cpu_online_mask);
cpuid = irq_rover;
raw_spin_unlock_irqrestore(&irq_rover_lock, flags);
} else {
cpuid = cpumask_first_and(mask, cpu_online_mask);
if (cpuid >= nr_cpu_ids)
goto do_round_robin;
}
return get_hard_smp_processor_id(cpuid);
}
#else
int irq_choose_cpu(const struct cpumask *mask)
{
return hard_smp_processor_id();
}
#endif
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