KVM: arm64: Move RESx into individual register descriptors

Instead of hacking the RES1 bits at runtime, move them into the
register descriptors. This makes it significantly nicer.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260202184329.2724080-14-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/kvm/config.c

@@ -28,6 +28,7 @@ struct reg_bits_to_feat_map {
 #define	REQUIRES_E2H1	BIT(5)	/* Add HCR_EL2.E2H RES1 as a pre-condition */
 #define	RES1_WHEN_E2H0	BIT(6)	/* RES1 when E2H=0 and not supported */
 #define	RES1_WHEN_E2H1	BIT(7)	/* RES1 when E2H=1 and not supported */
+#define	FORCE_RESx	BIT(8)	/* Unconditional RESx */
 
 	unsigned long	flags;
 
@@ -87,6 +88,12 @@ struct reg_feat_map_desc {
 		.match = (fun),				\
 	}
 
+#define __NEEDS_FEAT_0(m, f, w, ...)			\
+	{						\
+		.w	= (m),				\
+		.flags = (f),				\
+	}
+
 #define __NEEDS_FEAT_FLAG(m, f, w, ...)			\
 	CONCATENATE(__NEEDS_FEAT_, COUNT_ARGS(__VA_ARGS__))(m, f, w, __VA_ARGS__)
 
@@ -105,10 +112,14 @@ struct reg_feat_map_desc {
  */
 #define NEEDS_FEAT(m, ...)	NEEDS_FEAT_FLAG(m, 0, __VA_ARGS__)
 
+/* Declare fixed RESx bits */
+#define FORCE_RES0(m)		NEEDS_FEAT_FLAG(m, FORCE_RESx)
+#define FORCE_RES1(m)		NEEDS_FEAT_FLAG(m, FORCE_RESx | AS_RES1)
+
 /*
- * Declare the dependency between a non-FGT register, a set of
- * feature, and the set of individual bits it contains. This generates
- * a struct reg_feat_map_desc.
+ * Declare the dependency between a non-FGT register, a set of features,
+ * and the set of individual bits it contains. This generates a struct
+ * reg_feat_map_desc.
  */
 #define DECLARE_FEAT_MAP(n, r, m, f)					\
 	struct reg_feat_map_desc n = {					\
@@ -1007,6 +1018,8 @@ static const struct reg_bits_to_feat_map hcr_feat_map[] = {
 		   HCR_EL2_TWEDEn,
 		   FEAT_TWED),
 	NEEDS_FEAT_FIXED(HCR_EL2_E2H, compute_hcr_e2h),
+	FORCE_RES0(HCR_EL2_RES0),
+	FORCE_RES1(HCR_EL2_RES1),
 };
 
 static const DECLARE_FEAT_MAP(hcr_desc, HCR_EL2,
@@ -1027,6 +1040,8 @@ static const struct reg_bits_to_feat_map sctlr2_feat_map[] = {
 		   SCTLR2_EL1_CPTM	|
 		   SCTLR2_EL1_CPTM0,
 		   FEAT_CPA2),
+	FORCE_RES0(SCTLR2_EL1_RES0),
+	FORCE_RES1(SCTLR2_EL1_RES1),
 };
 
 static const DECLARE_FEAT_MAP(sctlr2_desc, SCTLR2_EL1,
@@ -1052,6 +1067,8 @@ static const struct reg_bits_to_feat_map tcr2_el2_feat_map[] = {
 		   TCR2_EL2_E0POE,
 		   FEAT_S1POE),
 	NEEDS_FEAT(TCR2_EL2_PIE, FEAT_S1PIE),
+	FORCE_RES0(TCR2_EL2_RES0),
+	FORCE_RES1(TCR2_EL2_RES1),
 };
 
 static const DECLARE_FEAT_MAP(tcr2_el2_desc, TCR2_EL2,
@@ -1129,6 +1146,8 @@ static const struct reg_bits_to_feat_map sctlr_el1_feat_map[] = {
 		   SCTLR_EL1_A		|
 		   SCTLR_EL1_M,
 		   FEAT_AA64EL1),
+	FORCE_RES0(SCTLR_EL1_RES0),
+	FORCE_RES1(SCTLR_EL1_RES1),
 };
 
 static const DECLARE_FEAT_MAP(sctlr_el1_desc, SCTLR_EL1,
@@ -1163,6 +1182,8 @@ static const struct reg_bits_to_feat_map mdcr_el2_feat_map[] = {
 		   MDCR_EL2_TDE		|
 		   MDCR_EL2_TDRA,
 		   FEAT_AA64EL1),
+	FORCE_RES0(MDCR_EL2_RES0),
+	FORCE_RES1(MDCR_EL2_RES1),
 };
 
 static const DECLARE_FEAT_MAP(mdcr_el2_desc, MDCR_EL2,
@@ -1201,6 +1222,8 @@ static const struct reg_bits_to_feat_map vtcr_el2_feat_map[] = {
 		   VTCR_EL2_SL0		|
 		   VTCR_EL2_T0SZ,
 		   FEAT_AA64EL1),
+	FORCE_RES0(VTCR_EL2_RES0),
+	FORCE_RES1(VTCR_EL2_RES1),
 };
 
 static const DECLARE_FEAT_MAP(vtcr_el2_desc, VTCR_EL2,
@@ -1211,8 +1234,14 @@ static void __init check_feat_map(const struct reg_bits_to_feat_map *map,
 {
 	u64 mask = 0;
 
+	/*
+	 * Don't account for FORCE_RESx that are architectural, and
+	 * therefore part of the resx parameter. Other FORCE_RESx bits
+	 * are implementation choices, and therefore accounted for.
+	 */
 	for (int i = 0; i < map_size; i++)
-		mask |= map[i].bits;
+		if (!((map[i].flags & FORCE_RESx) && (map[i].bits & resx)))
+			mask |= map[i].bits;
 
 	if (mask != ~resx)
 		kvm_err("Undefined %s behaviour, bits %016llx\n",
@@ -1284,13 +1313,16 @@ static struct resx compute_resx_bits(struct kvm *kvm,
 		if (map[i].flags & exclude)
 			continue;
 
-		switch (map[i].flags & (CALL_FUNC | FIXED_VALUE)) {
+		switch (map[i].flags & (FORCE_RESx | CALL_FUNC | FIXED_VALUE)) {
 		case CALL_FUNC | FIXED_VALUE:
 			map[i].fval(kvm, &resx);
 			continue;
 		case CALL_FUNC:
 			match = map[i].match(kvm);
 			break;
+		case FORCE_RESx:
+			match = false;
+			break;
 		default:
 			match = idreg_feat_match(kvm, &map[i]);
 		}
@@ -1434,28 +1466,22 @@ struct resx get_reg_fixed_bits(struct kvm *kvm, enum vcpu_sysreg reg)
 		break;
 	case HCR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hcr_desc, 0, 0);
-		resx.res1 |= HCR_EL2_RES1;
 		break;
 	case SCTLR2_EL1:
 	case SCTLR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &sctlr2_desc, 0, 0);
-		resx.res1 |= SCTLR2_EL1_RES1;
 		break;
 	case TCR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &tcr2_el2_desc, 0, 0);
-		resx.res1 |= TCR2_EL2_RES1;
 		break;
 	case SCTLR_EL1:
 		resx = compute_reg_resx_bits(kvm, &sctlr_el1_desc, 0, 0);
-		resx.res1 |= SCTLR_EL1_RES1;
 		break;
 	case MDCR_EL2:
 		resx = compute_reg_resx_bits(kvm, &mdcr_el2_desc, 0, 0);
-		resx.res1 |= MDCR_EL2_RES1;
 		break;
 	case VTCR_EL2:
 		resx = compute_reg_resx_bits(kvm, &vtcr_el2_desc, 0, 0);
-		resx.res1 |= VTCR_EL2_RES1;
 		break;
 	default:
 		WARN_ON_ONCE(1);