[PATCH v4 24/26] irqchip/gic-v3: Add base support for pseudo-NMI
From: Julien Thierry
Date: Fri May 25 2018 - 08:00:18 EST
Provide a higher priority to be used for pseudo-NMIs. When such an
interrupt is received, enter the NMI state and prevent other NMIs to
be raised.
When returning from a pseudo-NMI, skip preemption and tracing if the
interrupted context has interrupts disabled.
Signed-off-by: Julien Thierry <julien.thierry@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm/include/asm/arch_gicv3.h | 6 ++++++
arch/arm64/include/asm/arch_gicv3.h | 6 ++++++
arch/arm64/kernel/entry.S | 43 +++++++++++++++++++++++++++++++++++++
drivers/irqchip/irq-gic-v3.c | 41 +++++++++++++++++++++++++++++++++++
4 files changed, 96 insertions(+)
diff --git a/arch/arm/include/asm/arch_gicv3.h b/arch/arm/include/asm/arch_gicv3.h
index b39d620..1ed0476 100644
--- a/arch/arm/include/asm/arch_gicv3.h
+++ b/arch/arm/include/asm/arch_gicv3.h
@@ -374,5 +374,11 @@ static inline void gic_start_pmr_masking(void)
WARN_ON(true);
}
+static inline void gic_set_nmi_active(void)
+{
+ /* Should not get called */
+ WARN_ON(true);
+}
+
#endif /* !__ASSEMBLY__ */
#endif /* !__ASM_ARCH_GICV3_H */
diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h
index 23c88ac0..3196cf1 100644
--- a/arch/arm64/include/asm/arch_gicv3.h
+++ b/arch/arm64/include/asm/arch_gicv3.h
@@ -166,5 +166,11 @@ static inline void gic_start_pmr_masking(void)
asm volatile ("msr daifclr, #2" : : : "memory");
}
+/* Notify an NMI is active, blocking other NMIs */
+static inline void gic_set_nmi_active(void)
+{
+ asm volatile ("msr daifset, #2" : : : "memory");
+}
+
#endif /* __ASSEMBLY__ */
#endif /* __ASM_ARCH_GICV3_H */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f56f27e..0d0c829 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -391,6 +391,16 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
mov sp, x19
.endm
+ /* Should be checked on return from irq handlers */
+ .macro branch_if_was_nmi, tmp, target
+ alternative_if ARM64_HAS_IRQ_PRIO_MASKING
+ mrs \tmp, daif
+ alternative_else
+ mov \tmp, #0
+ alternative_endif
+ tbnz \tmp, #7, \target // Exiting an NMI
+ .endm
+
/*
* These are the registers used in the syscall handler, and allow us to
* have in theory up to 7 arguments to a function - x0 to x6.
@@ -611,12 +621,30 @@ ENDPROC(el1_sync)
el1_irq:
kernel_entry 1
enable_da_f
+
#ifdef CONFIG_TRACE_IRQFLAGS
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ ldr x20, [sp, #S_PMR_SAVE]
+ /* Irqs were disabled, don't trace */
+ tbz x20, ICC_PMR_EL1_EN_SHIFT, 1f
+#endif
bl trace_hardirqs_off
+1:
#endif
irq_handler
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /*
+ * Irqs were disabled, we have an nmi.
+ * We might have interrupted a context with interrupt disabled that set
+ * NEED_RESCHED flag.
+ * Skip preemption and irq tracing if needed.
+ */
+ tbz x20, ICC_PMR_EL1_EN_SHIFT, untraced_irq_exit
+ branch_if_was_nmi x0, skip_preempt
+#endif
+
#ifdef CONFIG_PREEMPT
ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count
cbnz w24, 1f // preempt count != 0
@@ -625,9 +653,13 @@ el1_irq:
bl el1_preempt
1:
#endif
+
+skip_preempt:
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
+
+untraced_irq_exit:
kernel_exit 1
ENDPROC(el1_irq)
@@ -858,6 +890,9 @@ el0_irq_naked:
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
+
+ branch_if_was_nmi x2, nmi_ret_to_user
+
b ret_to_user
ENDPROC(el0_irq)
@@ -1353,3 +1388,11 @@ alternative_else_nop_endif
ENDPROC(__sdei_asm_handler)
NOKPROBE(__sdei_asm_handler)
#endif /* CONFIG_ARM_SDE_INTERFACE */
+
+/*
+ * NMI return path to EL0
+ */
+nmi_ret_to_user:
+ ldr x1, [tsk, #TSK_TI_FLAGS]
+ b finish_ret_to_user
+ENDPROC(nmi_ret_to_user)
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index b144f73..4be5996 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -41,6 +41,8 @@
#include "irq-gic-common.h"
+#define GICD_INT_NMI_PRI 0xa0
+
struct redist_region {
void __iomem *redist_base;
phys_addr_t phys_base;
@@ -253,6 +255,12 @@ static inline bool arch_uses_gic_prios(void)
return IS_ENABLED(CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS);
}
+static inline bool gic_supports_nmi(void)
+{
+ return arch_uses_gic_prios()
+ && static_branch_likely(&have_non_secure_prio_view);
+}
+
static int gic_irq_set_irqchip_state(struct irq_data *d,
enum irqchip_irq_state which, bool val)
{
@@ -371,6 +379,20 @@ static u64 gic_mpidr_to_affinity(unsigned long mpidr)
return aff;
}
+static void do_handle_nmi(unsigned int hwirq, struct pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+ unsigned int irq;
+
+ nmi_enter();
+
+ irq = irq_find_mapping(gic_data.domain, hwirq);
+ generic_handle_irq(irq);
+
+ nmi_exit();
+ set_irq_regs(old_regs);
+}
+
static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
{
u32 irqnr;
@@ -386,6 +408,23 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
int err;
+ if (gic_supports_nmi()
+ && unlikely(gic_read_rpr() == GICD_INT_NMI_PRI)) {
+ /*
+ * We need to prevent other NMIs to occur even after a
+ * priority drop.
+ * We keep I flag set until cpsr is restored from
+ * kernel_exit.
+ */
+ gic_set_nmi_active();
+
+ if (static_branch_likely(&supports_deactivate_key))
+ gic_write_eoir(irqnr);
+
+ do_handle_nmi(irqnr, regs);
+ return;
+ }
+
if (static_branch_likely(&supports_deactivate_key))
gic_write_eoir(irqnr);
else if (!arch_uses_gic_prios())
@@ -1183,6 +1222,8 @@ static int __init gic_init_bases(void __iomem *dist_base,
if (arch_uses_gic_prios()) {
if (!gic_has_group0() || gic_dist_security_disabled())
static_branch_enable(&have_non_secure_prio_view);
+ else
+ pr_warn("SCR_EL3.FIQ set, cannot enable use of pseudo-NMIs\n");
}
return 0;
--
1.9.1