arm64: Relax GIC version check during early boot

Updates to the GIC architecture allow ID_AA64PFR0_EL1.GIC to have
values other than 0 or 1. At the moment, Linux is quite strict in the
way it handles this field at early boot stage (cpufeature is fine) and
will refuse to use the system register CPU interface if it doesn't
find the value 1.

Fixes: 021f653791ad17e03f98aaa7fb933816ae16f161 ("irqchip: gic-v3: Initial support for GICv3")
Reported-by: Chase Conklin <Chase.Conklin@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 15d79a8..eecf792 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -539,8 +539,7 @@ set_hcr:
        /* GICv3 system register access */
        mrs     x0, id_aa64pfr0_el1
        ubfx    x0, x0, #24, #4
-       cmp     x0, #1
-       b.ne    3f
+       cbz     x0, 3f
 
        mrs_s   x0, SYS_ICC_SRE_EL2
        orr     x0, x0, #ICC_SRE_EL2_SRE        // Set ICC_SRE_EL2.SRE==1