Re: [PATCH v6 15/24] arm64: Switch to PMR masking when starting CPUs
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2018-12-04 17:51:49
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On Mon, Nov 12, 2018 at 11:57:06AM +0000, Julien Thierry wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 8dc9dde..e495360 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c@@ -35,6 +35,7 @@ #include <linux/smp.h> #include <linux/seq_file.h> #include <linux/irq.h> +#include <linux/irqchip/arm-gic-v3.h> #include <linux/percpu.h> #include <linux/clockchips.h> #include <linux/completion.h>@@ -175,6 +176,25 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) return ret; } +static void init_gic_priority_masking(void) +{ + u32 gic_sre = gic_read_sre(); + u32 cpuflags; + + if (WARN_ON(!(gic_sre & ICC_SRE_EL1_SRE))) + return; + + WARN_ON(!irqs_disabled()); + + gic_write_pmr(GIC_PRIO_IRQOFF); + + cpuflags = read_sysreg(daif); + + /* We can only unmask PSR.I if we can take aborts */ + if (!(cpuflags & PSR_A_BIT)) + write_sysreg(cpuflags & ~PSR_I_BIT, daif);
I don't understand this. If you don't switch off PSR_I_BIT here, where does it happen? In which scenario do we actually have the A bit still set? At a quick look, smp_prepare_boot_cpu() would have the A bit cleared previously by setup_arch(). We have secondary_start_kernel() where you call init_gic_priority_masking() before local_daif_restore(). So what happens if you always turn off PSR_I_BIT here? -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel