arm/arm64: KVM: MMIO support for BE guest

Do the necessary byteswap when host and guest have different
views of the universe. Actually, the only case we need to take
care of is when the guest is BE. All the other cases are naturally
handled.

Also be careful about endianness when the data is being memcopy-ed
from/to the run buffer.

Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index eec073875218..b016577e37a4 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -177,4 +177,52 @@ static inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
         return kvm_vcpu_get_hsr(vcpu) & ESR_EL2_FSC_TYPE;
 }
 
+static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
+{
+        if (vcpu_mode_is_32bit(vcpu))
+                return !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_E_BIT);
+
+        return !!(vcpu_sys_reg(vcpu, SCTLR_EL1) & (1 << 25));
+}
+
+static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
+                                                    unsigned long data,
+                                                    unsigned int len)
+{
+        if (kvm_vcpu_is_be(vcpu)) {
+                switch (len) {
+                case 1:
+                        return data & 0xff;
+                case 2:
+                        return be16_to_cpu(data & 0xffff);
+                case 4:
+                        return be32_to_cpu(data & 0xffffffff);
+                default:
+                        return be64_to_cpu(data);
+                }
+        }
+
+        return data;            /* Leave LE untouched */
+}
+
+static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
+                                                    unsigned long data,
+                                                    unsigned int len)
+{
+        if (kvm_vcpu_is_be(vcpu)) {
+                switch (len) {
+                case 1:
+                        return data & 0xff;
+                case 2:
+                        return cpu_to_be16(data & 0xffff);
+                case 4:
+                        return cpu_to_be32(data & 0xffffffff);
+                default:
+                        return cpu_to_be64(data);
+                }
+        }
+
+        return data;            /* Leave LE untouched */
+}
+
 #endif /* __ARM64_KVM_EMULATE_H__ */