xtensa: make fake NMI configurable

Do not always use fake NMI when safe, provide Kconfig option instead.
Print a warning if fake NMI is chosen in unsafe configuration, but allow
it, because it may work if the user knows that interrupts with
priorities at or above PMM IRQ are not used. Add a check to NMI handler
that BUGs if any of these IRQs fire.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 82044f73232335f715a1356ae61f7d66dc538f51..128e63d3a6329bf993d3d0a41905657720c2ac9a 100644 (file)
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -139,6 +139,22 @@ config XTENSA_VARIANT_HAVE_PERF_EVENTS
 
          If unsure, say N.
 
+config XTENSA_FAKE_NMI
+       bool "Treat PMM IRQ as NMI"
+       depends on XTENSA_VARIANT_HAVE_PERF_EVENTS
+       default n
+       help
+         If PMM IRQ is the only IRQ at EXCM level it is safe to
+         treat it as NMI, which improves accuracy of profiling.
+
+         If there are other interrupts at or above PMM IRQ priority level
+         but not above the EXCM level, PMM IRQ still may be treated as NMI,
+         but only if these IRQs are not used. There will be a build warning
+         saying that this is not safe, and a bugcheck if one of these IRQs
+         actually fire.
+
+         If unsure, say N.
+
 config XTENSA_UNALIGNED_USER
        bool "Unaligned memory access in use space"
        help

diff --git a/arch/xtensa/include/asm/processor.h b/arch/xtensa/include/asm/processor.h
index 83e2e4bc01ba24f54965df8b4ee3de7855e028e0..744ecf0dc3a4f51c441732493f29ab977ae572ea 100644 (file)
--- a/arch/xtensa/include/asm/processor.h
+++ b/arch/xtensa/include/asm/processor.h
@@ -78,22 +78,20 @@
 #define XTENSA_INTLEVEL_MASK(level) _XTENSA_INTLEVEL_MASK(level)
 #define _XTENSA_INTLEVEL_MASK(level) (XCHAL_INTLEVEL##level##_MASK)
 
-#define IS_POW2(v) (((v) & ((v) - 1)) == 0)
+#define XTENSA_INTLEVEL_ANDBELOW_MASK(l) _XTENSA_INTLEVEL_ANDBELOW_MASK(l)
+#define _XTENSA_INTLEVEL_ANDBELOW_MASK(l) (XCHAL_INTLEVEL##l##_ANDBELOW_MASK)
 
 #define PROFILING_INTLEVEL XTENSA_INT_LEVEL(XCHAL_PROFILING_INTERRUPT)
 
 /* LOCKLEVEL defines the interrupt level that masks all
  * general-purpose interrupts.
  */
-#if defined(CONFIG_XTENSA_VARIANT_HAVE_PERF_EVENTS) && \
-       defined(XCHAL_PROFILING_INTERRUPT) && \
-       PROFILING_INTLEVEL == XCHAL_EXCM_LEVEL && \
-       XCHAL_EXCM_LEVEL > 1 && \
-       IS_POW2(XTENSA_INTLEVEL_MASK(PROFILING_INTLEVEL))
-#define LOCKLEVEL (XCHAL_EXCM_LEVEL - 1)
+#if defined(CONFIG_XTENSA_FAKE_NMI) && defined(XCHAL_PROFILING_INTERRUPT)
+#define LOCKLEVEL (PROFILING_INTLEVEL - 1)
 #else
 #define LOCKLEVEL XCHAL_EXCM_LEVEL
 #endif
+
 #define TOPLEVEL XCHAL_EXCM_LEVEL
 #define XTENSA_FAKE_NMI (LOCKLEVEL < TOPLEVEL)
 

diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 42d441f7898b94db35e3a2cd55af500f23f6435a..be0cae8082c71be5d42c6b5ecf02991cd67c7ec6 100644 (file)
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -205,6 +205,32 @@ extern void do_IRQ(int, struct pt_regs *);
 
 #if XTENSA_FAKE_NMI
 
+#define IS_POW2(v) (((v) & ((v) - 1)) == 0)
+
+#if !(PROFILING_INTLEVEL == XCHAL_EXCM_LEVEL && \
+      IS_POW2(XTENSA_INTLEVEL_MASK(PROFILING_INTLEVEL)))
+#warning "Fake NMI is requested for PMM, but there are other IRQs at or above its level."
+#warning "Fake NMI will be used, but there will be a bugcheck if one of those IRQs fire."
+
+static inline void check_valid_nmi(void)
+{
+       unsigned intread = get_sr(interrupt);
+       unsigned intenable = get_sr(intenable);
+
+       BUG_ON(intread & intenable &
+              ~(XTENSA_INTLEVEL_ANDBELOW_MASK(PROFILING_INTLEVEL) ^
+                XTENSA_INTLEVEL_MASK(PROFILING_INTLEVEL) ^
+                BIT(XCHAL_PROFILING_INTERRUPT)));
+}
+
+#else
+
+static inline void check_valid_nmi(void)
+{
+}
+
+#endif
+
 irqreturn_t xtensa_pmu_irq_handler(int irq, void *dev_id);
 
 DEFINE_PER_CPU(unsigned long, nmi_count);
@@ -219,6 +245,7 @@ void do_nmi(struct pt_regs *regs)
        old_regs = set_irq_regs(regs);
        nmi_enter();
        ++*this_cpu_ptr(&nmi_count);
+       check_valid_nmi();
        xtensa_pmu_irq_handler(0, NULL);
        nmi_exit();
        set_irq_regs(old_regs);