Subject: [PATCH 1/2] KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts

From: Marc Zyngier <[email-masked]>
Date: Tue, 9 Jun 2020 09:49:20 +0100

AArch32 CP1x registers are overlayed on their AArch64 counterparts
in the vcpu struct. This leads to an interesting problem as they
are stored in their CPU-local format, and thus a CP1x register
doesn't "hit" the lower 32bit portion of the AArch64 register on
a BE host.

To workaround this unfortunate situation, introduce a bias trick
in the vcpu_cp1x() accessors which picks the correct half of the
64bit register.

Cc: [email-masked]
Reported-by: James Morse <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/include/asm/kvm_host.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 59029e90b557..e80c0e06f235 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -404,8 +404,14 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg);
  * CP14 and CP15 live in the same array, as they are backed by the
  * same system registers.
  */
-#define vcpu_cp14(v,r)		((v)->arch.ctxt.copro[(r)])
-#define vcpu_cp15(v,r)		((v)->arch.ctxt.copro[(r)])
+#ifdef CPU_BIG_ENDIAN
+#define CPx_OFFSET	1
+#else
+#define CPx_OFFSET	0
+#endif
+
+#define vcpu_cp14(v,r)		((v)->arch.ctxt.copro[(r) ^ CPx_OFFSET])
+#define vcpu_cp15(v,r)		((v)->arch.ctxt.copro[(r) ^ CPx_OFFSET])
 
 struct kvm_vm_stat {
 	ulong remote_tlb_flush;
-- 
2.26.2

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