[PATCH] ARM: virt: enable GICv3 system registers

[Jean-Philippe Brucker]

ARMv8 introduces system registers for the Generic Interrupt Controller's
CPU and virtual interfaces.
When GICv3 is implemented, EL2 needs to allow the kernel to use those
registers, by changing the value of ICC_HSRE.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm/kernel/hyp-stub.S |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
index 2a55373..0b1e4a9 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S
@@ -17,6 +17,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/irqchip/arm-gic-v3.h>
 #include <linux/linkage.h>
 #include <asm/assembler.h>
 #include <asm/virt.h>
@@ -161,6 +162,29 @@ ARM_BE8(orr	r7, r7, #(1 << 25))     @ HSCTLR.EE
 1:
 #endif
 
+#ifdef CONFIG_ARM_GIC_V3
+	@ Check whether GICv3 system registers are available
+	mrc	p15, 0, r7, c0, c1, 1	@ ID_PFR1
+	ubfx	r7, r7, #28, #4
+	cmp	r7, #1
+	bne	2f
+
+	@ Enable system register accesses
+	mrc	p15, 4, r7, c12, c9, 5	@ ICC_HSRE
+	orr	r7, r7, #(ICC_SRE_EL2_ENABLE | ICC_SRE_EL2_SRE)
+	mcr	p15, 4, r7, c12, c9, 5	@ ICC_HSRE
+	isb
+
+	@ SRE bit could be forced to 0 by firmware.
+	@ Check whether it sticks before accessing any other sysreg
+	mrc	p15, 4, r7, c12, c9, 5	@ ICC_HSRE
+	tst	r7, #ICC_SRE_EL2_SRE
+	beq	2f
+	mov	r7, #0
+	mcr	p15, 4, r7, c12, c11, 0	@ ICH_HCR
+2:
+#endif
+
 	bx	lr			@ The boot CPU mode is left in r4.
 ENDPROC(__hyp_stub_install_secondary)
 
-- 
1.7.9.5