linux-kernel - [PATCH v5 3/5] KVM: selftests: Expand set of APIs for pinning tasks to a single CPU

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Message-ID: <20250626001225.744268-4-seanjc@google.com>
Date: Wed, 25 Jun 2025 17:12:23 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v5 3/5] KVM: selftests: Expand set of APIs for pinning tasks
 to a single CPU

Expand kvm_pin_this_task_to_pcpu() into a set of APIs to allow pinning a
task (or self) to a CPU (any or specific).  This will allow deduplicating
code throughout a variety of selftests.

Opportunistically use "self" instead of "this_task" as it is both more
concise and less ambiguous.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../testing/selftests/kvm/include/kvm_util.h  | 31 ++++++++++++++++++-
 tools/testing/selftests/kvm/lib/kvm_util.c    | 15 +++++----
 tools/testing/selftests/kvm/lib/memstress.c   |  2 +-
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 91908d4a6edf..23a506d7eca3 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -21,6 +21,8 @@
 #include <sys/eventfd.h>
 #include <sys/ioctl.h>
 
+#include <pthread.h>
+
 #include "kvm_util_arch.h"
 #include "kvm_util_types.h"
 #include "sparsebit.h"
@@ -1054,7 +1056,34 @@ struct kvm_vcpu *vm_recreate_with_one_vcpu(struct kvm_vm *vm);
 
 void kvm_set_files_rlimit(uint32_t nr_vcpus);
 
-void kvm_pin_this_task_to_pcpu(uint32_t pcpu);
+int __pin_task_to_cpu(pthread_t task, int cpu);
+
+static inline void pin_task_to_cpu(pthread_t task, int cpu)
+{
+	int r;
+
+	r = __pin_task_to_cpu(task, cpu);
+	TEST_ASSERT(!r, "Failed to set thread affinity to pCPU '%u'", cpu);
+}
+
+static inline int pin_task_to_any_cpu(pthread_t task)
+{
+	int cpu = sched_getcpu();
+
+	pin_task_to_cpu(task, cpu);
+	return cpu;
+}
+
+static inline void pin_self_to_cpu(int cpu)
+{
+	pin_task_to_cpu(pthread_self(), cpu);
+}
+
+static inline int pin_self_to_any_cpu(void)
+{
+	return pin_task_to_any_cpu(pthread_self());
+}
+
 void kvm_print_vcpu_pinning_help(void);
 void kvm_parse_vcpu_pinning(const char *pcpus_string, uint32_t vcpu_to_pcpu[],
 			    int nr_vcpus);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 90f90f1c194f..c3f5142b0a54 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -620,15 +620,14 @@ struct kvm_vcpu *vm_recreate_with_one_vcpu(struct kvm_vm *vm)
 	return vm_vcpu_recreate(vm, 0);
 }
 
-void kvm_pin_this_task_to_pcpu(uint32_t pcpu)
+int __pin_task_to_cpu(pthread_t task, int cpu)
 {
-	cpu_set_t mask;
-	int r;
+	cpu_set_t cpuset;
 
-	CPU_ZERO(&mask);
-	CPU_SET(pcpu, &mask);
-	r = sched_setaffinity(0, sizeof(mask), &mask);
-	TEST_ASSERT(!r, "sched_setaffinity() failed for pCPU '%u'.", pcpu);
+	CPU_ZERO(&cpuset);
+	CPU_SET(cpu, &cpuset);
+
+	return pthread_setaffinity_np(task, sizeof(cpuset), &cpuset);
 }
 
 static uint32_t parse_pcpu(const char *cpu_str, const cpu_set_t *allowed_mask)
@@ -682,7 +681,7 @@ void kvm_parse_vcpu_pinning(const char *pcpus_string, uint32_t vcpu_to_pcpu[],
 
 	/* 2. Check if the main worker needs to be pinned. */
 	if (cpu) {
-		kvm_pin_this_task_to_pcpu(parse_pcpu(cpu, &allowed_mask));
+		pin_self_to_cpu(parse_pcpu(cpu, &allowed_mask));
 		cpu = strtok(NULL, delim);
 	}
 
diff --git a/tools/testing/selftests/kvm/lib/memstress.c b/tools/testing/selftests/kvm/lib/memstress.c
index 313277486a1d..557c0a0a5658 100644
--- a/tools/testing/selftests/kvm/lib/memstress.c
+++ b/tools/testing/selftests/kvm/lib/memstress.c
@@ -265,7 +265,7 @@ static void *vcpu_thread_main(void *data)
 	int vcpu_idx = vcpu->vcpu_idx;
 
 	if (memstress_args.pin_vcpus)
-		kvm_pin_this_task_to_pcpu(memstress_args.vcpu_to_pcpu[vcpu_idx]);
+		pin_self_to_cpu(memstress_args.vcpu_to_pcpu[vcpu_idx]);
 
 	WRITE_ONCE(vcpu->running, true);
 
-- 
2.50.0.727.gbf7dc18ff4-goog