arm64/vmm: Add HYP_FEAT_FGT{,2}

Add the macros and detection for Fine-grained traps (FEAT_FGT and
FEAT_FGT2).

Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D54686

sys/arm64/vmm/arm64.h

@@ -131,6 +131,8 @@ struct hyp {
 	uint64_t	feats;		/* Which features are enabled */
 #define	HYP_FEAT_HCX		(0x1ul << 0)
 #define	HYP_FEAT_ECV_POFF	(0x1ul << 1)
+#define	HYP_FEAT_FGT		(0x1ul << 2)
+#define	HYP_FEAT_FGT2		(0x1ul << 3)
 	bool		vgic_attached;
 	struct vgic_v3	*vgic;
 	struct hypctx	*ctx[];

sys/arm64/vmm/vmm_arm64.c

@@ -525,6 +525,18 @@ vmmops_init(struct vm *vm, pmap_t pmap)
 	if (get_kernel_reg(ID_AA64MMFR0_EL1, &idreg)) {
 		if (ID_AA64MMFR0_ECV_VAL(idreg) >= ID_AA64MMFR0_ECV_POFF)
 			hyp->feats |= HYP_FEAT_ECV_POFF;
+
+		switch (ID_AA64MMFR0_FGT_VAL(idreg)) {
+		case ID_AA64MMFR0_FGT_NONE:
+			break;
+		default:
+		case ID_AA64MMFR0_FGT_8_9:
+			hyp->feats |= HYP_FEAT_FGT2;
+			/* FALLTHROUGH */
+		case ID_AA64MMFR0_FGT_8_6:
+			hyp->feats |= HYP_FEAT_FGT;
+			break;
+		}
 	}
 
 	if (get_kernel_reg(ID_AA64MMFR1_EL1, &idreg)) {