On 29/04/2019 17:00, Julien Thierry wrote:
> Using IRQ priority masking to enable/disable interrupts is a bit
> sensitive as it requires to deal with both ICC_PMR_EL1 and PSR.I.
>
> Introduce some validity checks to both highlight the states in which
> functions dealing with IRQ enabling/disabling can (not) be called, and
> bark a warning when called in an unexpected state.
>
> Since these checks are done on hotpaths, introduce a build option to
> choose whether to do the checking.
>
> Signed-off-by: Julien Thierry <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Will Deacon <[email protected]>
> ---
> arch/arm64/Kconfig | 11 +++++++++++
> arch/arm64/include/asm/daifflags.h | 9 +++++++++
> arch/arm64/include/asm/irqflags.h | 14 ++++++++++++++
> 3 files changed, 34 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 7e34b9e..3fb38f3 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1359,6 +1359,17 @@ config ARM64_PSEUDO_NMI
>
> If unsure, say N
>
> +if ARM64_PSEUDO_NMI
> +config ARM64_DEBUG_PRIORITY_MASKING
> + bool "Debug interrupt priority masking"
> + help
> + This adds runtime checks to functions enabling/disabling
> + interrupts when using priority masking. The additional checks verify
> + the validity of ICC_PMR_EL1 when calling concerned functions.
> +
> + If unsure, say N
> +endif
> +
> config RELOCATABLE
> bool
> help
> diff --git a/arch/arm64/include/asm/daifflags.h
> b/arch/arm64/include/asm/daifflags.h
> index a32ece9..9512968 100644
> --- a/arch/arm64/include/asm/daifflags.h
> +++ b/arch/arm64/include/asm/daifflags.h
> @@ -28,6 +28,11 @@
> /* mask/save/unmask/restore all exceptions, including interrupts. */
> static inline void local_daif_mask(void)
> {
> + WARN_ON(IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
> + system_uses_irq_prio_masking() &&
Given that you repeat these conditions all over the place, how about a
helper:
#define DEBUG_PRIORITY_MASKING_CHECK(x) \
(IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) && \
system_uses_irq_prio_masking() && (x))
or some variant thereof.
> + (read_sysreg_s(SYS_ICC_PMR_EL1) == (GIC_PRIO_IRQOFF |
> + GIC_PRIO_IGNORE_PMR)));
> +
> asm volatile(
> "msr daifset, #0xf // local_daif_mask\n"
> :
> @@ -62,6 +67,10 @@ static inline void local_daif_restore(unsigned long flags)
> {
> bool irq_disabled = flags & PSR_I_BIT;
>
> + WARN_ON(IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
> + system_uses_irq_prio_masking() &&
> + !(read_sysreg(daif) & PSR_I_BIT));
> +
> if (!irq_disabled) {
> trace_hardirqs_on();
>
> diff --git a/arch/arm64/include/asm/irqflags.h
> b/arch/arm64/include/asm/irqflags.h
> index 516cdfc..a40abc2 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -40,6 +40,13 @@
> */
> static inline void arch_local_irq_enable(void)
> {
> + if (IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
> + system_uses_irq_prio_masking()) {
> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
> +
> + WARN_ON(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
> + }
> +
> asm volatile(ALTERNATIVE(
> "msr daifclr, #2 // arch_local_irq_enable\n"
> "nop",
> @@ -53,6 +60,13 @@ static inline void arch_local_irq_enable(void)
>
> static inline void arch_local_irq_disable(void)
> {
> + if (IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
> + system_uses_irq_prio_masking()) {
> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
> +
> + WARN_ON(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
> + }
> +
> asm volatile(ALTERNATIVE(
> "msr daifset, #2 // arch_local_irq_disable",
> "msr_s " __stringify(SYS_ICC_PMR_EL1) ", %0",
> --
> 1.9.1
>
nit: There is also the question of using WARN_ON in a context that will
be extremely noisy if we're in a condition where this fires.
WARN_ON_ONCE, maybe? This is a debugging thing, so maybe we just don't care.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
