From 380b0e5e0e30e0ae57056cd18e5a9a60892b2ece Mon Sep 17 00:00:00 2001 From: Josh Hilke Date: Fri, 26 Jun 2026 14:35:23 -0700 Subject: [PATCH] KVM: selftests: Add a helper to set proc IRQ affinity for IRQ test Add a utility, proc_irq_set_smp_affinity(), to set the CPU affinity of a Linux host IRQ via the proc filesystem. Use smp_affinity_list instead of smp_affinity to avoid having to convert the single CPU to a bitmask. The helper will be used by the eventfd IRQ test to verify delivery of IRQs when the affinity is randomized/modified. Signed-off-by: Josh Hilke [sean: make the utility self-contained, drop "list", massage changelog] Link: https://patch.msgid.link/20260626213534.3866178-11-seanjc@google.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/include/proc_util.h | 2 ++ tools/testing/selftests/kvm/lib/proc_util.c | 14 ++++++++++++++ 2 files changed, 16 insertions(+) diff --git a/tools/testing/selftests/kvm/include/proc_util.h b/tools/testing/selftests/kvm/include/proc_util.h index 704839b6d7af..d1ddc967d11d 100644 --- a/tools/testing/selftests/kvm/include/proc_util.h +++ b/tools/testing/selftests/kvm/include/proc_util.h @@ -6,4 +6,6 @@ unsigned int vfio_msix_to_host_irq(const char *vfio_device_bdf, int msix); +void proc_irq_set_smp_affinity(unsigned int irq, int cpu); + #endif /* SELFTEST_KVM_PROC_UTIL_H */ diff --git a/tools/testing/selftests/kvm/lib/proc_util.c b/tools/testing/selftests/kvm/lib/proc_util.c index 84d30f055a0a..3960b3841d63 100644 --- a/tools/testing/selftests/kvm/lib/proc_util.c +++ b/tools/testing/selftests/kvm/lib/proc_util.c @@ -38,3 +38,17 @@ unsigned int vfio_msix_to_host_irq(const char *device_bdf, int msix) return (unsigned int)irq; } +void proc_irq_set_smp_affinity(unsigned int irq, int cpu) +{ + char path[PATH_MAX]; + int r, fd; + + snprintf(path, sizeof(path), "/proc/irq/%u/smp_affinity_list", irq); + fd = open(path, O_RDWR); + TEST_ASSERT(fd >= 0, "Failed to open %s", path); + + r = dprintf(fd, "%d\n", cpu); + TEST_ASSERT(r > 0, "Failed to affinitize IRQ-%u to CPU %d", irq, cpu); + + kvm_close(fd); +}