[RFC 6/7] arm64: Detect current view of GIC priorities
Julien Thierry
julien.thierry at arm.com
Wed Oct 11 06:01:01 PDT 2017
The values non secure EL1 needs to use for priority registers depends on
the value of SCR_EL3.FIQ.
Since we don't have access to SCR_EL3, we fake an interrupt and compare the
GIC priority with the one present in the [re]distributor.
Also, add firmware requirements related to SCR_EL3.
Signed-off-by: Julien Thierry <julien.thierry at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Jason Cooper <jason at lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier at arm.com>
---
Documentation/arm64/booting.txt | 5 +++
arch/arm64/include/asm/arch_gicv3.h | 5 +++
arch/arm64/include/asm/irqflags.h | 6 +++
arch/arm64/include/asm/sysreg.h | 1 +
drivers/irqchip/irq-gic-v3.c | 83 +++++++++++++++++++++++++++++++++++++
5 files changed, 100 insertions(+)
diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
index 8d0df62..e387938 100644
--- a/Documentation/arm64/booting.txt
+++ b/Documentation/arm64/booting.txt
@@ -188,6 +188,11 @@ Before jumping into the kernel, the following conditions must be met:
the kernel image will be entered must be initialised by software at a
higher exception level to prevent execution in an UNKNOWN state.
+ - SCR_EL3.FIQ must have the same value across all CPUs the kernel is
+ executing on.
+ - The value of SCR_EL3.FIQ must be the same as the one present at boot
+ time whenever the kernel is executing.
+
For systems with a GICv3 interrupt controller to be used in v3 mode:
- If EL3 is present:
ICC_SRE_EL3.Enable (bit 3) must be initialiased to 0b1.
diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h
index b6b430c..90a3dc3 100644
--- a/arch/arm64/include/asm/arch_gicv3.h
+++ b/arch/arm64/include/asm/arch_gicv3.h
@@ -114,6 +114,11 @@ static inline void gic_write_bpr1(u32 val)
write_sysreg_s(val, SYS_ICC_BPR1_EL1);
}
+static inline u32 gic_read_rpr(void)
+{
+ return read_sysreg_s(SYS_ICC_RPR_EL1);
+}
+
#define gic_read_typer(c) readq_relaxed(c)
#define gic_write_irouter(v, c) writeq_relaxed(v, c)
#define gic_read_lpir(c) readq_relaxed(c)
diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
index 1c69ebb..4718ca3f 100644
--- a/arch/arm64/include/asm/irqflags.h
+++ b/arch/arm64/include/asm/irqflags.h
@@ -205,6 +205,12 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
!(ARCH_FLAGS_GET_PMR(flags) & ICC_PMR_EL1_EN_BIT);
}
+/* Mask IRQs at CPU level instead of GIC level */
+static inline void arch_irqs_daif_disable(void)
+{
+ asm volatile ("msr daifset, #2" : : : "memory");
+}
+
void maybe_switch_to_sysreg_gic_cpuif(void);
#endif /* CONFIG_IRQFLAGS_GIC_MASKING */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index f707fed..e71bc81 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -205,6 +205,7 @@
#define SYS_ICC_SRE_EL1 sys_reg(3, 0, 12, 12, 5)
#define SYS_ICC_IGRPEN0_EL1 sys_reg(3, 0, 12, 12, 6)
#define SYS_ICC_IGRPEN1_EL1 sys_reg(3, 0, 12, 12, 7)
+#define SYS_ICC_RPR_EL1 sys_reg(3, 0, 12, 11, 3)
#define SYS_CONTEXTIDR_EL1 sys_reg(3, 0, 13, 0, 1)
#define SYS_TPIDR_EL1 sys_reg(3, 0, 13, 0, 4)
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 1cdf495..e0b235f 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -62,6 +62,10 @@ struct gic_chip_data {
static struct gic_chip_data gic_data __read_mostly;
static struct static_key supports_deactivate = STATIC_KEY_INIT_TRUE;
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+DEFINE_STATIC_KEY_FALSE(have_non_secure_prio_view);
+#endif
+
static struct gic_kvm_info gic_v3_kvm_info;
#define gic_data_rdist() (this_cpu_ptr(gic_data.rdists.rdist))
@@ -969,6 +973,81 @@ static int partition_domain_translate(struct irq_domain *d,
.select = gic_irq_domain_select,
};
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+/*
+ * The behaviours of RPR and PMR registers differ depending on the value of
+ * SCR_EL3.FIQ, while the behaviour of priority registers of the distributor
+ * and redistributors is always the same.
+ *
+ * If SCR_EL3.FIQ == 1, the values used for RPR and PMR are the same as the ones
+ * programmed in the distributor and redistributors registers.
+ *
+ * Otherwise, the value presented by RPR as well as the value which will be
+ * compared against PMR is: (GIC_(R)DIST_PRI[irq] >> 1) | 0x80;
+ *
+ * see GICv3/GICv4 Architecture Specification (IHI0069D):
+ * - section 4.8.1 Non-secure accesses to register fields for Secure interrupt
+ * priorities.
+ * - Figure 4-7 Secure read of the priority field for a Non-secure Group 1
+ * interrupt.
+ */
+static void __init gic_detect_prio_view(void)
+{
+ /*
+ * Randomly picked SGI, must be <= 8 as other SGIs might be
+ * used by the firmware.
+ */
+ const u32 fake_irqnr = 7;
+ const u32 fake_irqmask = BIT(fake_irqnr);
+ void __iomem * const rdist_base = gic_data_rdist_sgi_base();
+ unsigned long irq_flags;
+ u32 acked_irqnr;
+ bool was_enabled;
+
+ irq_flags = arch_local_save_flags();
+
+ arch_irqs_daif_disable();
+
+ was_enabled = !!(readl_relaxed(rdist_base + GICD_ISENABLER) &
+ fake_irqmask);
+
+ if (!was_enabled)
+ writel_relaxed(fake_irqmask, rdist_base + GICD_ISENABLER);
+
+ /* Need to unmask to acknowledge the IRQ */
+ gic_write_pmr(ICC_PMR_EL1_UNMASKED);
+ dsb(sy);
+
+ /* Fake a pending SGI */
+ writel_relaxed(fake_irqmask, rdist_base + GICD_ISPENDR);
+ dsb(sy);
+
+ acked_irqnr = gic_read_iar();
+
+ if (acked_irqnr == fake_irqnr) {
+ if (gic_read_rpr() == gic_get_irq_prio(acked_irqnr, rdist_base))
+ static_branch_enable(&have_non_secure_prio_view);
+ } else {
+ pr_warn("Unexpected IRQ for priority detection: %u\n",
+ acked_irqnr);
+ }
+
+ if (acked_irqnr < 1020) {
+ gic_write_eoir(acked_irqnr);
+ if (static_key_true(&supports_deactivate))
+ gic_write_dir(acked_irqnr);
+ }
+
+ /* Restore enabled state */
+ if (!was_enabled) {
+ writel_relaxed(fake_irqmask, rdist_base + GICD_ICENABLER);
+ gic_redist_wait_for_rwp();
+ }
+
+ arch_local_irq_restore(irq_flags);
+}
+#endif
+
static int __init gic_init_bases(void __iomem *dist_base,
struct redist_region *rdist_regs,
u32 nr_redist_regions,
@@ -1025,6 +1104,10 @@ static int __init gic_init_bases(void __iomem *dist_base,
gic_cpu_init();
gic_cpu_pm_init();
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ gic_detect_prio_view();
+#endif
+
return 0;
out_free:
--
1.9.1
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