KVM: selftests: Add SMT control state helper

Move the SMT control check out of the hyperv_cpuid selftest so that it
is generally accessible all KVM selftests. Split the functionality into
a helper that populates a buffer with SMT control value which other
helpers can use to ascertain if SMT state is available and active.

Signed-off-by: Pratik R. Sampat <prsampat@amd.com>
Link: https://lore.kernel.org/r/20250305230000.231025-5-prsampat@amd.com
[sean: prepend is_ to the helpers]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 373912464fb4..a1fc52bbdf7a 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -549,6 +549,41 @@ void kvm_get_stat(struct kvm_binary_stats *stats, const char *name,
 #define vm_get_stat(vm, stat) __get_stat(&(vm)->stats, stat)
 #define vcpu_get_stat(vcpu, stat) __get_stat(&(vcpu)->stats, stat)
 
+static inline bool read_smt_control(char *buf, size_t buf_size)
+{
+	FILE *f = fopen("/sys/devices/system/cpu/smt/control", "r");
+	bool ret;
+
+	if (!f)
+		return false;
+
+	ret = fread(buf, sizeof(*buf), buf_size, f) > 0;
+	fclose(f);
+
+	return ret;
+}
+
+static inline bool is_smt_possible(void)
+{
+	char buf[16];
+
+	if (read_smt_control(buf, sizeof(buf)) &&
+	    (!strncmp(buf, "forceoff", 8) || !strncmp(buf, "notsupported", 12)))
+		return false;
+
+	return true;
+}
+
+static inline bool is_smt_on(void)
+{
+	char buf[16];
+
+	if (read_smt_control(buf, sizeof(buf)) && !strncmp(buf, "on", 2))
+		return true;
+
+	return false;
+}
+
 void vm_create_irqchip(struct kvm_vm *vm);
 
 static inline int __vm_create_guest_memfd(struct kvm_vm *vm, uint64_t size,