[PATCH] KVM: arm64: GICv3: Check the implementation before accessing ICH_VTR_EL2

[Marc Zyngier]

The ICH_HCR_EL2 patching code is generally GIC implementation agnostic,
except when checking for broken Apple HW, which imposes to read
ICH_VTR_EL2.

It is therefore important to check whether we are running on such
HW before reading this register, as it will otherwise UNDEF when
run on HW that doesn't have GICv3.

Reported-by: Marek Szyprowski <m.szyprowski at samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
Fixes: ca30799f7c2d ("KVM: arm64: Turn vgic-v3 errata traps into a patched-in constant")
Closes: https://lore.kernel.org/r/b618732b-fd26-49e0-84c5-bfd54be09cd2@samsung.com
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic-v3.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index fc7a4cb8e231d..598621b14a30d 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -829,8 +829,8 @@ static const struct midr_range broken_seis[] = {
 static bool vgic_v3_broken_seis(void)
 {
 	return (is_kernel_in_hyp_mode() &&
-		(read_sysreg_s(SYS_ICH_VTR_EL2) & ICH_VTR_EL2_SEIS) &&
-		is_midr_in_range_list(broken_seis));
+		is_midr_in_range_list(broken_seis) &&
+		(read_sysreg_s(SYS_ICH_VTR_EL2) & ICH_VTR_EL2_SEIS));
 }
 
 void noinstr kvm_compute_ich_hcr_trap_bits(struct alt_instr *alt,
-- 
2.47.3