mips/kvm: Fix ABI for use of 64-bit registers.

All registers are 64-bits wide, 32-bit guests use the least
significant portion of the register storage fields.

Signed-off-by: David Daney <david.daney@cavium.com>
Acked-by: Sanjay Lal <sanjayl@kymasys.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/include/uapi/asm/kvm.h

@@ -18,12 +18,18 @@
 #define N_MIPS_COPROC_REGS      32
 #define N_MIPS_COPROC_SEL   	8
 
-/* for KVM_GET_REGS and KVM_SET_REGS */
+/*
+ * for KVM_GET_REGS and KVM_SET_REGS
+ *
+ * If Config[AT] is zero (32-bit CPU), the register contents are
+ * stored in the lower 32-bits of the struct kvm_regs fields and sign
+ * extended to 64-bits.
+ */
 struct kvm_regs {
-	__u32 gprs[32];
-	__u32 hi;
-	__u32 lo;
-	__u32 pc;
+	__u64 gprs[32];
+	__u64 hi;
+	__u64 lo;
+	__u64 pc;
 
 	__u32 cp0reg[N_MIPS_COPROC_REGS][N_MIPS_COPROC_SEL];
 };