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Subject[PATCH v5 21/27] arm64: Switch to PMR masking when starting CPUs
Date
Once the boot CPU has been prepared or a new secondary CPU has been
brought up, use ICC_PMR_EL1 to mask interrupts on that CPU and clear
PSR.I bit.

Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/irqflags.h | 3 +++
arch/arm64/kernel/head.S | 35 +++++++++++++++++++++++++++++++++++
arch/arm64/kernel/smp.c | 5 +++++
3 files changed, 43 insertions(+)

diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
index 193cfd0..d31e9b6 100644
--- a/arch/arm64/include/asm/irqflags.h
+++ b/arch/arm64/include/asm/irqflags.h
@@ -153,5 +153,8 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
return (ARCH_FLAGS_GET_DAIF(flags) & (PSR_I_BIT)) |
!(ARCH_FLAGS_GET_PMR(flags) & ICC_PMR_EL1_EN_BIT);
}
+
+void maybe_switch_to_sysreg_gic_cpuif(void);
+
#endif
#endif
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b085306..ba73690 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -648,6 +648,41 @@ set_cpu_boot_mode_flag:
ENDPROC(set_cpu_boot_mode_flag)

/*
+ * void maybe_switch_to_sysreg_gic_cpuif(void)
+ *
+ * Enable interrupt controller system register access if this feature
+ * has been detected by the alternatives system.
+ *
+ * Before we jump into generic code we must enable interrupt controller system
+ * register access because this is required by the irqflags macros. We must
+ * also mask interrupts at the PMR and unmask them within the PSR. That leaves
+ * us set up and ready for the kernel to make its first call to
+ * arch_local_irq_enable().
+ *
+ */
+ENTRY(maybe_switch_to_sysreg_gic_cpuif)
+alternative_if_not ARM64_HAS_IRQ_PRIO_MASKING
+ b 1f
+alternative_else
+ mrs_s x0, SYS_ICC_SRE_EL1
+alternative_endif
+ orr x0, x0, #1
+ msr_s SYS_ICC_SRE_EL1, x0 // Set ICC_SRE_EL1.SRE==1
+ isb // Make sure SRE is now set
+ mrs x0, daif
+ tbz x0, #7, no_mask_pmr // Are interrupts on?
+ mov x0, ICC_PMR_EL1_MASKED
+ msr_s SYS_ICC_PMR_EL1, x0 // Prepare for unmask of I bit
+ msr daifclr, #2 // Clear the I bit
+ b 1f
+no_mask_pmr:
+ mov x0, ICC_PMR_EL1_UNMASKED
+ msr_s SYS_ICC_PMR_EL1, x0
+1:
+ ret
+ENDPROC(maybe_switch_to_sysreg_gic_cpuif)
+
+/*
* These values are written with the MMU off, but read with the MMU on.
* Writers will invalidate the corresponding address, discarding up to a
* 'Cache Writeback Granule' (CWG) worth of data. The linker script ensures
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 22c9a0a..443fa2b 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -185,6 +185,8 @@ asmlinkage notrace void secondary_start_kernel(void)
struct mm_struct *mm = &init_mm;
unsigned int cpu;

+ maybe_switch_to_sysreg_gic_cpuif();
+
cpu = task_cpu(current);
set_my_cpu_offset(per_cpu_offset(cpu));

@@ -421,6 +423,9 @@ void __init smp_prepare_boot_cpu(void)
* and/or scheduling is enabled.
*/
apply_boot_alternatives();
+
+ /* Conditionally switch to GIC PMR for interrupt masking */
+ maybe_switch_to_sysreg_gic_cpuif();
}

static u64 __init of_get_cpu_mpidr(struct device_node *dn)
--
1.9.1
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