@@ -34,6 +34,7 @@
#define ICC_CTLR __ACCESS_CP15(c12, 0, c12, 4)
#define ICC_SRE __ACCESS_CP15(c12, 0, c12, 5)
#define ICC_IGRPEN1 __ACCESS_CP15(c12, 0, c12, 7)
+#define ICC_BPR1 __ACCESS_CP15(c12, 0, c12, 3)
#define ICC_HSRE __ACCESS_CP15(c12, 4, c9, 5)
@@ -157,6 +158,11 @@ static inline void gic_write_sre(u32 val)
isb();
}
+static inline void gic_write_bpr1(u32 val)
+{
+ asm volatile("mcr " __stringify(ICC_BPR1) : : "r" (val));
+}
+
/*
* Even in 32bit systems that use LPAE, there is no guarantee that the I/O
* interface provides true 64bit atomic accesses, so using strd/ldrd doesn't
@@ -28,6 +28,7 @@
#define ICC_CTLR_EL1 sys_reg(3, 0, 12, 12, 4)
#define ICC_SRE_EL1 sys_reg(3, 0, 12, 12, 5)
#define ICC_GRPEN1_EL1 sys_reg(3, 0, 12, 12, 7)
+#define ICC_BPR1_EL1 sys_reg(3, 0, 12, 12, 3)
#define ICC_SRE_EL2 sys_reg(3, 4, 12, 9, 5)
@@ -165,6 +166,11 @@ static inline void gic_write_sre(u32 val)
isb();
}
+static inline void gic_write_bpr1(u32 val)
+{
+ asm volatile("msr_s " __stringify(ICC_BPR1_EL1) ", %0" : : "r" (val));
+}
+
#define gic_read_typer(c) readq_relaxed(c)
#define gic_write_irouter(v, c) writeq_relaxed(v, c)
@@ -495,6 +495,14 @@ static void gic_cpu_sys_reg_init(void)
/* Set priority mask register */
gic_write_pmr(DEFAULT_PMR_VALUE);
+ /*
+ * Some firmwares hand over to the kernel with the BPR changed from
+ * its reset value (and with a value large enough to prevent
+ * any pre-emptive interrupts from working at all). Writing a zero
+ * to BPR restores is reset value.
+ */
+ gic_write_bpr1(0);
+
if (static_key_true(&supports_deactivate)) {
/* EOI drops priority only (mode 1) */
gic_write_ctlr(ICC_CTLR_EL1_EOImode_drop);
Currently, when running on FVP, CPU 0 boots up with its BPR changed from the reset value. This renders it impossible to (preemptively) prioritize interrupts on CPU 0. This is harmless on normal systems since Linux typically does not support preemptive interrupts. It does however cause problems in systems with additional changes (such as patches for NMI simulation). Many thanks to Andrew Thoelke for suggesting the BPR as having the potential to harm preemption. Suggested-by: Andrew Thoelke <andrew.thoelke@arm.com> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> --- arch/arm/include/asm/arch_gicv3.h | 6 ++++++ arch/arm64/include/asm/arch_gicv3.h | 6 ++++++ drivers/irqchip/irq-gic-v3.c | 8 ++++++++ 3 files changed, 20 insertions(+) -- 2.7.4