[PATCH 4.9 030/118] arm64: Relax GIC version check during early boot

From: Greg Kroah-Hartman
Date: Fri Mar 22 2019 - 09:03:15 EST

4.9-stable review patch. If anyone has any objections, please let me know.


[ Upstream commit 74698f6971f25d045301139413578865fc2bd8f9 ]

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@xxxxxxx>
Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
arch/arm64/kernel/head.S | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 3289d1458791..db6ff1944c41 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -534,8 +534,7 @@ 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, ICC_SRE_EL2
orr x0, x0, #ICC_SRE_EL2_SRE // Set ICC_SRE_EL2.SRE==1