KVM: arm64: Add AArch32 mapping annotation

In order to deal with the few AArch32 system registers that map to
only a particular half of their AArch64 counterpart (such as DFAR
and IFAR being colocated in FAR_EL1), let's add an optional annotation
to the sysreg descriptor structure, indicating whether a register
maps to the upper or lower 32bits of a register.

Nothing is using these annotation yet.
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/sys_regs.h

@@ -27,6 +27,12 @@ struct sys_reg_desc {
 	/* Sysreg string for debug */
 	const char *name;
 
+	enum {
+		AA32_ZEROHIGH,
+		AA32_LO,
+		AA32_HI,
+	} aarch32_map;
+
 	/* MRS/MSR instruction which accesses it. */
 	u8	Op0;
 	u8	Op1;
@@ -153,6 +159,7 @@ const struct sys_reg_desc *find_reg_by_id(u64 id,
 					  const struct sys_reg_desc table[],
 					  unsigned int num);
 
+#define AA32(_x)	.aarch32_map = AA32_##_x
 #define Op0(_x) 	.Op0 = _x
 #define Op1(_x) 	.Op1 = _x
 #define CRn(_x)		.CRn = _x