KVM: arm64: selftests: Remove ARM64_FEATURE_FIELD_BITS and its last user

ARM64_FEATURE_FIELD_BITS is set to 4 but not all ID register fields are 4
bits. See for instance ID_AA64SMFR0_EL1. The last user of this define,
ARM64_FEATURE_FIELD_BITS, is the set_id_regs selftest. Its logic assumes
the fields aren't a single bits; assert that's the case and stop using the
define. As there are no more users, ARM64_FEATURE_FIELD_BITS is removed
from the arm64 tools sysreg.h header. A separate commit removes this from
the kernel version of the header.

Signed-off-by: Ben Horgan <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
Acked-by: Oliver Upton <[e-mail]>
Signed-off-by: Catalin Marinas <[e-mail]>

tools/arch/arm64/include/asm/sysreg.h

···
 #define GCS_CAP(x)	((((unsigned long)x) & GCS_CAP_ADDR_MASK) | \
 					       GCS_CAP_VALID_TOKEN)
 
-#define ARM64_FEATURE_FIELD_BITS	4
-
 #ifdef __ASSEMBLY__
 
 	.macro	mrs_s, rt, sreg

tools/testing/selftests/kvm/arm64/set_id_regs.c

···
 /* Return a safe value to a given ftr_bits an ftr value */
 uint64_t get_safe_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 {
-	uint64_t ftr_max = GENMASK_ULL(ARM64_FEATURE_FIELD_BITS - 1, 0);
+	uint64_t ftr_max = ftr_bits->mask >> ftr_bits->shift;
+
+	TEST_ASSERT(ftr_max > 1, "This test doesn't support single bit features");
 
 	if (ftr_bits->sign == FTR_UNSIGNED) {
 		switch (ftr_bits->type) {
···
 /* Return an invalid value to a given ftr_bits an ftr value */
 uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 {
-	uint64_t ftr_max = GENMASK_ULL(ARM64_FEATURE_FIELD_BITS - 1, 0);
+	uint64_t ftr_max = ftr_bits->mask >> ftr_bits->shift;
+
+	TEST_ASSERT(ftr_max > 1, "This test doesn't support single bit features");
 
 	if (ftr_bits->sign == FTR_UNSIGNED) {
 		switch (ftr_bits->type) {