[PATCH v2 02/10] KVM: arm64: Add reg_feat_map_desc to describe full register dependency

[Marc Zyngier]

struct reg_bits_to_feat_map is great to describe bit-to-feature
dependency, but not so much to describe register-to-feature
dependency. Yet both need to exist.

Add a new reg_feat_map_desc structure to describe this.

Extra complexity is added by the need to source the RES0 bits from
the runtime-computed FGT masks, for which we need an extra flag
and extra complexity. Oh well.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/config.c | 81 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 72 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
index d85dd05c00b0e..c2bfffe660bca 100644
--- a/arch/arm64/kvm/config.c
+++ b/arch/arm64/kvm/config.c
@@ -7,12 +7,22 @@
 #include <linux/kvm_host.h>
 #include <asm/sysreg.h>
 
+/*
+ * Describes the dependencies between a set of bits (or the negation
+ * of a set of RES0 bits) and a feature. The flags indicate how the
+ * data is interpreted.
+ */
 struct reg_bits_to_feat_map {
-	u64		bits;
+	union {
+		u64	bits;
+		u64	*res0p;
+	};
 
 #define	NEVER_FGU	BIT(0)	/* Can trap, but never UNDEF */
 #define	CALL_FUNC	BIT(1)	/* Needs to evaluate tons of crap */
 #define	FIXED_VALUE	BIT(2)	/* RAZ/WI or RAO/WI in KVM */
+#define	RES0_POINTER	BIT(3)	/* Pointer to RES0 value instead of bits */
+
 	unsigned long	flags;
 
 	union {
@@ -28,9 +38,27 @@ struct reg_bits_to_feat_map {
 	};
 };
 
-#define __NEEDS_FEAT_3(m, f, id, fld, lim)		\
+/*
+ * Describes the dependencies for a given register:
+ *
+ * @feat_map describes the dependency for the whole register. If the
+ * features the register depends on are not present, the whole
+ * register is effectively RES0.
+ *
+ * @bit_feat_map describes the dependencies for a set of bits in that
+ * register. If the features these bits depend on are not present, the
+ * bits are effectively RES0.
+ */
+struct reg_feat_map_desc {
+	const char			  *name;
+	const struct reg_bits_to_feat_map feat_map;
+	const struct reg_bits_to_feat_map *bit_feat_map;
+	const unsigned int		  bit_feat_map_sz;
+};
+
+#define __NEEDS_FEAT_3(m, f, w, id, fld, lim)		\
 	{						\
-		.bits	= (m),				\
+		.w	= (m),				\
 		.flags = (f),				\
 		.regidx	= IDREG_IDX(SYS_ ## id),	\
 		.shift	= id ##_## fld ## _SHIFT,	\
@@ -39,28 +67,63 @@ struct reg_bits_to_feat_map {
 		.lo_lim	= id ##_## fld ##_## lim	\
 	}
 
-#define __NEEDS_FEAT_2(m, f, fun, dummy)		\
+#define __NEEDS_FEAT_2(m, f, w, fun, dummy)		\
 	{						\
-		.bits	= (m),				\
+		.w	= (m),				\
 		.flags = (f) | CALL_FUNC,		\
 		.fval = (fun),				\
 	}
 
-#define __NEEDS_FEAT_1(m, f, fun)			\
+#define __NEEDS_FEAT_1(m, f, w, fun)			\
 	{						\
-		.bits	= (m),				\
+		.w	= (m),				\
 		.flags = (f) | CALL_FUNC,		\
 		.match = (fun),				\
 	}
 
+#define __NEEDS_FEAT_FLAG(m, f, w, ...)			\
+	CONCATENATE(__NEEDS_FEAT_, COUNT_ARGS(__VA_ARGS__))(m, f, w, __VA_ARGS__)
+
 #define NEEDS_FEAT_FLAG(m, f, ...)			\
-	CONCATENATE(__NEEDS_FEAT_, COUNT_ARGS(__VA_ARGS__))(m, f, __VA_ARGS__)
+	__NEEDS_FEAT_FLAG(m, f, bits, __VA_ARGS__)
 
 #define NEEDS_FEAT_FIXED(m, ...)			\
-	NEEDS_FEAT_FLAG(m, FIXED_VALUE, __VA_ARGS__, 0)
+	__NEEDS_FEAT_FLAG(m, FIXED_VALUE, bits, __VA_ARGS__, 0)
+
+#define NEEDS_FEAT_RES0(p, ...)				\
+	__NEEDS_FEAT_FLAG(p, RES0_POINTER, res0p, __VA_ARGS__)
 
+/*
+ * Declare the dependency between a set of bits and a set of features,
+ * generating a struct reg_bit_to_feat_map.
+ */
 #define NEEDS_FEAT(m, ...)	NEEDS_FEAT_FLAG(m, 0, __VA_ARGS__)
 
+/*
+ * 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.
+ */
+#define DECLARE_FEAT_MAP(n, r, m, f)					\
+	struct reg_feat_map_desc n = {					\
+		.name			= #r,				\
+		.feat_map		= NEEDS_FEAT(~r##_RES0, f), 	\
+		.bit_feat_map		= m,				\
+		.bit_feat_map_sz	= ARRAY_SIZE(m),		\
+	}
+
+/*
+ * Specialised version of the above for FGT registers that have their
+ * RES0 masks described as struct fgt_masks.
+ */
+#define DECLARE_FEAT_MAP_FGT(n, msk, m, f)				\
+	struct reg_feat_map_desc n = {					\
+		.name			= #msk,				\
+		.feat_map		= NEEDS_FEAT_RES0(&msk.res0, f),\
+		.bit_feat_map		= m,				\
+		.bit_feat_map_sz	= ARRAY_SIZE(m),		\
+	}
+
 #define FEAT_SPE		ID_AA64DFR0_EL1, PMSVer, IMP
 #define FEAT_SPE_FnE		ID_AA64DFR0_EL1, PMSVer, V1P2
 #define FEAT_BRBE		ID_AA64DFR0_EL1, BRBE, IMP
-- 
2.39.2