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SubjectRe: [PATCH v6 10/24] arm64: irqflags: Use ICC_PMR_EL1 for interrupt masking
On Mon, Nov 12, 2018 at 11:57:01AM +0000, Julien Thierry wrote:
> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
> index 24692ed..e0a32e4 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -18,7 +18,27 @@
>
> #ifdef __KERNEL__
>
> +#include <asm/alternative.h>
> +#include <asm/cpufeature.h>
> #include <asm/ptrace.h>
> +#include <asm/sysreg.h>
> +
> +
> +/*
> + * When ICC_PMR_EL1 is used for interrupt masking, only the bit indicating
> + * whether the normal interrupts are masked is kept along with the daif
> + * flags.
> + */
> +#define ARCH_FLAG_PMR_EN 0x1
> +
> +#define MAKE_ARCH_FLAGS(daif, pmr) \
> + ((daif) | (((pmr) >> GIC_PRIO_STATUS_SHIFT) & ARCH_FLAG_PMR_EN))
> +
> +#define ARCH_FLAGS_GET_PMR(flags) \
> + ((((flags) & ARCH_FLAG_PMR_EN) << GIC_PRIO_STATUS_SHIFT) \
> + | GIC_PRIO_IRQOFF)
> +
> +#define ARCH_FLAGS_GET_DAIF(flags) ((flags) & ~ARCH_FLAG_PMR_EN)

I wonder whether we could just use the PSR_I_BIT here to decide whether
to set the GIC_PRIO_IRQ{ON,OFF}. We could clear the PSR_I_BIT in
_restore_daif() with an alternative.

> +/*
> + * CPU interrupt mask handling.
> + */
> static inline void arch_local_irq_enable(void)
> {
> - asm volatile(
> - "msr daifclr, #2 // arch_local_irq_enable"
> - :
> + unsigned long unmasked = GIC_PRIO_IRQON;
> +
> + asm volatile(ALTERNATIVE(
> + "msr daifclr, #2 // arch_local_irq_enable\n"
> + "nop",
> + "msr_s " __stringify(SYS_ICC_PMR_EL1) ",%0\n"
> + "dsb sy",
> + ARM64_HAS_IRQ_PRIO_MASKING)

DSB needed here as well? I guess I'd have to read the GIC spec before
asking again ;).

--
Catalin

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