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SubjectRe: [PATCH v3 6/8] arm64: irqflags: Introduce explicit debugging for IRQ priorities
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On 06/06/2019 10:31, 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 <julien.thierry@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> ---
> arch/arm64/Kconfig | 11 +++++++++++
> arch/arm64/include/asm/cpufeature.h | 6 ++++++
> arch/arm64/include/asm/daifflags.h | 7 +++++++
> arch/arm64/include/asm/irqflags.h | 14 +++++++++++++-
> 4 files changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 697ea05..8acc40e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1436,6 +1436,17 @@ 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/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index bc895c8..693a086 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -617,6 +617,12 @@ static inline bool system_uses_irq_prio_masking(void)
> cpus_have_const_cap(ARM64_HAS_IRQ_PRIO_MASKING);
> }
>
> +static inline bool system_has_prio_mask_debugging(void)
> +{
> + return IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
> + system_uses_irq_prio_masking();
> +}
> +
> #define ARM64_SSBD_UNKNOWN -1
> #define ARM64_SSBD_FORCE_DISABLE 0
> #define ARM64_SSBD_KERNEL 1
> diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
> index f93204f..eca5bee 100644
> --- a/arch/arm64/include/asm/daifflags.h
> +++ b/arch/arm64/include/asm/daifflags.h
> @@ -28,6 +28,10 @@
> /* mask/save/unmask/restore all exceptions, including interrupts. */
> static inline void local_daif_mask(void)
> {
> + WARN_ON(system_has_prio_mask_debugging() &&
> + (read_sysreg_s(SYS_ICC_PMR_EL1) == (GIC_PRIO_IRQOFF |
> + GIC_PRIO_PSR_I_SET)));
> +
> asm volatile(
> "msr daifset, #0xf // local_daif_mask\n"
> :
> @@ -62,6 +66,9 @@ static inline void local_daif_restore(unsigned long flags)
> {
> bool irq_disabled = flags & PSR_I_BIT;
>
> + WARN_ON(system_has_prio_mask_debugging() &&
> + !(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 b6f757f..cac2d2a 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -40,6 +40,12 @@
> */
> static inline void arch_local_irq_enable(void)
> {
> + if (system_has_prio_mask_debugging()) {
> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
> +
> + WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
> + }
> +
> asm volatile(ALTERNATIVE(
> "msr daifclr, #2 // arch_local_irq_enable\n"
> "nop",
> @@ -53,6 +59,12 @@ static inline void arch_local_irq_enable(void)
>
> static inline void arch_local_irq_disable(void)
> {
> + if (system_has_prio_mask_debugging()) {
> + u32 pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
> +
> + WARN_ON_ONCE(pmr != GIC_PRIO_IRQON && pmr != GIC_PRIO_IRQOFF);
> + }
> +
> asm volatile(ALTERNATIVE(
> "msr daifset, #2 // arch_local_irq_disable",
> __msr_s(SYS_ICC_PMR_EL1, "%0"),
> @@ -86,7 +98,7 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
>
> asm volatile(ALTERNATIVE(
> "and %w0, %w1, #" __stringify(PSR_I_BIT),
> - "eor %w0, %w1, #" __stringify(GIC_PRIO_IRQOFF),
> + "eor %w0, %w1, #" __stringify(GIC_PRIO_IRQON),

Err... Which version is the correct one? This one, or the previous one?

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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