[PATCH v1 3/6] KVM: arm64: Add build validation for trap mask values

[Fuad Tabba]

These checks help ensure that all the bits are accounted for, and
that there hasn't been a transcribing error from the spec.

Signed-off-by: Fuad Tabba <tabba at google.com>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index f99d8af0b9af..2c6e8cbbd081 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -79,6 +79,16 @@ static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
 		clr |= ~hfg & __ ## reg ## _nMASK; 			\
 	} while(0)
 
+/*
+ * Validate the fine grain trap masks.
+ * Check that the masks do not overlap and that all bits are accounted for.
+ */
+#define CHECK_FGT_MASKS(reg)							\
+	do {									\
+		BUILD_BUG_ON((__ ## reg ## _MASK) & (__ ## reg ## _nMASK));	\
+		BUILD_BUG_ON(~((__ ## reg ## _RES0) ^ (__ ## reg ## _MASK) ^	\
+			       (__ ## reg ## _nMASK)));				\
+	} while(0)
 
 static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 {
@@ -86,6 +96,14 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 	u64 r_clr = 0, w_clr = 0, r_set = 0, w_set = 0, tmp;
 	u64 r_val, w_val;
 
+	CHECK_FGT_MASKS(HFGRTR_EL2);
+	CHECK_FGT_MASKS(HFGWTR_EL2);
+	CHECK_FGT_MASKS(HFGITR_EL2);
+	CHECK_FGT_MASKS(HDFGRTR_EL2);
+	CHECK_FGT_MASKS(HDFGWTR_EL2);
+	CHECK_FGT_MASKS(HAFGRTR_EL2);
+	CHECK_FGT_MASKS(HCRX_EL2);
+
 	if (!cpus_have_final_cap(ARM64_HAS_FGT))
 		return;
 
-- 
2.43.0.rc2.451.g8631bc7472-goog