2 files changed, 64 insertions, 7 deletions

diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
index 8df9f4658d6f..fbab7e21d116 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/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 5a703ae09ce5..eb9d9486f90b 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -66,6 +66,31 @@ struct gic_chip_data {
 static struct gic_chip_data gic_data __read_mostly;
 static DEFINE_STATIC_KEY_TRUE(supports_deactivate_key);
 
+/*
+ * The behaviours of RPR and PMR registers differ depending on the value of
+ * SCR_EL3.FIQ, and the behaviour of non-secure priority registers of the
+ * distributor and redistributors depends on whether security is enabled in the
+ * GIC.
+ *
+ * When security is enabled, non-secure priority values from the (re)distributor
+ * are presented to the GIC CPUIF as follow:
+ *     (GIC_(R)DIST_PRI[irq] >> 1) | 0x80;
+ *
+ * If SCR_EL3.FIQ == 1, the values writen to/read from PMR and RPR at non-secure
+ * EL1 are subject to a similar operation thus matching the priorities presented
+ * from the (re)distributor when security is enabled.
+ *
+ * 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.
+ *
+ * For now, we only support pseudo-NMIs if we have non-secure view of
+ * priorities.
+ */
+static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis);
+
 static struct gic_kvm_info gic_v3_kvm_info;
 static DEFINE_PER_CPU(bool, has_rss);
 
@@ -232,6 +257,12 @@ static void gic_unmask_irq(struct irq_data *d)
         gic_poke_irq(d, GICD_ISENABLER);
 }
 
+static inline bool gic_supports_nmi(void)
+{
+        return IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) &&
+               static_branch_likely(&supports_pseudo_nmis);
+}
+
 static int gic_irq_set_irqchip_state(struct irq_data *d,
                                      enum irqchip_irq_state which, bool val)
 {
@@ -573,6 +604,12 @@ static void gic_update_vlpi_properties(void)
                 !gic_data.rdists.has_direct_lpi ? "no " : "");
 }
 
+/* Check whether it's single security state view */
+static inline bool gic_dist_security_disabled(void)
+{
+        return readl_relaxed(gic_data.dist_base + GICD_CTLR) & GICD_CTLR_DS;
+}
+
 static void gic_cpu_sys_reg_init(void)
 {
         int i, cpu = smp_processor_id();
@@ -596,8 +633,17 @@ static void gic_cpu_sys_reg_init(void)
         group0 = gic_has_group0();
 
         /* Set priority mask register */
-        if (!gic_prio_masking_enabled())
+        if (!gic_prio_masking_enabled()) {
                 write_gicreg(DEFAULT_PMR_VALUE, ICC_PMR_EL1);
+        } else {
+                /*
+                 * Mismatch configuration with boot CPU, the system is likely
+                 * to die as interrupt masking will not work properly on all
+                 * CPUs
+                 */
+                WARN_ON(gic_supports_nmi() && group0 &&
+                        !gic_dist_security_disabled());
+        }
 
         /*
          * Some firmwares hand over to the kernel with the BPR changed from
@@ -852,12 +898,6 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 #endif
 
 #ifdef CONFIG_CPU_PM
-/* Check whether it's single security state view */
-static bool gic_dist_security_disabled(void)
-{
-        return readl_relaxed(gic_data.dist_base + GICD_CTLR) & GICD_CTLR_DS;
-}
-
 static int gic_cpu_pm_notifier(struct notifier_block *self,
                                unsigned long cmd, void *v)
 {
@@ -1110,6 +1150,11 @@ static bool gic_enable_quirk_msm8996(void *data)
         return true;
 }
 
+static void gic_enable_nmi_support(void)
+{
+        static_branch_enable(&supports_pseudo_nmis);
+}
+
 static int __init gic_init_bases(void __iomem *dist_base,
                                  struct redist_region *rdist_regs,
                                  u32 nr_redist_regions,
@@ -1179,6 +1224,13 @@ static int __init gic_init_bases(void __iomem *dist_base,
                 its_cpu_init();
         }
 
+        if (gic_prio_masking_enabled()) {
+                if (!gic_has_group0() || gic_dist_security_disabled())
+                        gic_enable_nmi_support();
+                else
+                        pr_warn("SCR_EL3.FIQ is cleared, cannot enable use of pseudo-NMIs\n");
+        }
+
         return 0;
 
 out_free: