[v2,11/38] arm64: Use build-time assertions for cpucap ordering

Commit Message

Mark Rutland Oct. 5, 2023, 9:49 a.m. UTC

Both sme2_kernel_enable() and fa64_kernel_enable() need to run after
sme_kernel_enable(). This happens to be true today as ARM64_SME has a
lower index than either ARM64_SME2 or ARM64_SME_FA64, and both functions
have a comment to this effect.

It would be nicer to have a build-time assertion like we for for
can_use_gic_priorities() and has_gic_prio_relaxed_sync(), as that way
it will be harder to miss any potential breakage.

This patch replaces the comments with build-time assertions.

Signed-off-by: Mark Rutland <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Suzuki K Poulose <[e-mail]>
Cc: Will Deacon <[e-mail]>
---
 arch/arm64/kernel/fpsimd.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

Patch

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 601b973f90ad2..48338cf8f90bd 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1310,23 +1310,21 @@  void sme_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
 	isb();
 }
 
-/*
- * This must be called after sme_kernel_enable(), we rely on the
- * feature table being sorted to ensure this.
- */
 void sme2_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
 {
+	/* This must be enabled after SME */
+	BUILD_BUG_ON(ARM64_SME2 <= ARM64_SME);
+
 	/* Allow use of ZT0 */
 	write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_EZT0_MASK,
 		       SYS_SMCR_EL1);
 }
 
-/*
- * This must be called after sme_kernel_enable(), we rely on the
- * feature table being sorted to ensure this.
- */
 void fa64_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
 {
+	/* This must be enabled after SME */
+	BUILD_BUG_ON(ARM64_SME_FA64 <= ARM64_SME);
+
 	/* Allow use of FA64 */
 	write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_FA64_MASK,
 		       SYS_SMCR_EL1);