[PATCH v2 07/12] KVM: arm64: Add build validation for FGT trap mask values

Fuad Tabba
2023-12-06T10:06:03Z

These checks help ensure that all the bits are accounted for,
that there hasn't been a transcribing error from the spec nor
from the generated mask values, which will be used in subsequent
patches.

Signed-off-by: Fuad Tabba <tabba@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 76a3d78b13d9..91d0f73161bd 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