KVM: selftests: Use canonical $(ARCH) paths for KVM selftests directories

Use the kernel's canonical $(ARCH) paths instead of the raw target triple
for KVM selftests directories.  KVM selftests are quite nearly the only
place in the entire kernel that using the target triple for directories,
tools/testing/selftests/drivers/s390x being the lone holdout.

Using the kernel's preferred nomenclature eliminates the minor, but
annoying, friction of having to translate to KVM's selftests directories,
e.g. for pattern matching, opening files, running selftests, etc.

Opportunsitically delete file comments that reference the full path of the
file, as they are obviously prone to becoming stale, and serve no known
purpose.

Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20241128005547.4077116-16-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 110 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/x86/tsc_scaling_sync.c b/tools/testing/selftests/kvm/x86/tsc_scaling_sync.c
new file mode 100644
index 000000000000..59c7304f805e
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/tsc_scaling_sync.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright © 2021 Amazon.com, Inc. or its affiliates.
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#include <stdint.h>
+#include <time.h>
+#include <sched.h>
+#include <signal.h>
+#include <pthread.h>
+
+#define NR_TEST_VCPUS 20
+
+static struct kvm_vm *vm;
+pthread_spinlock_t create_lock;
+
+#define TEST_TSC_KHZ    2345678UL
+#define TEST_TSC_OFFSET 200000000
+
+uint64_t tsc_sync;
+static void guest_code(void)
+{
+	uint64_t start_tsc, local_tsc, tmp;
+
+	start_tsc = rdtsc();
+	do {
+		tmp = READ_ONCE(tsc_sync);
+		local_tsc = rdtsc();
+		WRITE_ONCE(tsc_sync, local_tsc);
+		if (unlikely(local_tsc < tmp))
+			GUEST_SYNC_ARGS(0, local_tsc, tmp, 0, 0);
+
+	} while (local_tsc - start_tsc < 5000 * TEST_TSC_KHZ);
+
+	GUEST_DONE();
+}
+
+
+static void *run_vcpu(void *_cpu_nr)
+{
+	unsigned long vcpu_id = (unsigned long)_cpu_nr;
+	unsigned long failures = 0;
+	static bool first_cpu_done;
+	struct kvm_vcpu *vcpu;
+
+	/* The kernel is fine, but vm_vcpu_add() needs locking */
+	pthread_spin_lock(&create_lock);
+
+	vcpu = vm_vcpu_add(vm, vcpu_id, guest_code);
+
+	if (!first_cpu_done) {
+		first_cpu_done = true;
+		vcpu_set_msr(vcpu, MSR_IA32_TSC, TEST_TSC_OFFSET);
+	}
+
+	pthread_spin_unlock(&create_lock);
+
+	for (;;) {
+                struct ucall uc;
+
+		vcpu_run(vcpu);
+		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+		switch (get_ucall(vcpu, &uc)) {
+                case UCALL_DONE:
+			goto out;
+
+                case UCALL_SYNC:
+			printf("Guest %d sync %lx %lx %ld\n", vcpu->id,
+			       uc.args[2], uc.args[3], uc.args[2] - uc.args[3]);
+			failures++;
+			break;
+
+                default:
+                        TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+	}
+ out:
+	return (void *)failures;
+}
+
+int main(int argc, char *argv[])
+{
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_TSC_CONTROL));
+
+	vm = vm_create(NR_TEST_VCPUS);
+	vm_ioctl(vm, KVM_SET_TSC_KHZ, (void *) TEST_TSC_KHZ);
+
+	pthread_spin_init(&create_lock, PTHREAD_PROCESS_PRIVATE);
+	pthread_t cpu_threads[NR_TEST_VCPUS];
+	unsigned long cpu;
+	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++)
+		pthread_create(&cpu_threads[cpu], NULL, run_vcpu, (void *)cpu);
+
+	unsigned long failures = 0;
+	for (cpu = 0; cpu < NR_TEST_VCPUS; cpu++) {
+		void *this_cpu_failures;
+		pthread_join(cpu_threads[cpu], &this_cpu_failures);
+		failures += (unsigned long)this_cpu_failures;
+	}
+
+	TEST_ASSERT(!failures, "TSC sync failed");
+	pthread_spin_destroy(&create_lock);
+	kvm_vm_free(vm);
+	return 0;
+}