Add a selftest to verify that eventfd+irqfd bindings are globally unique, i.e. that KVM doesn't allow multiple irqfds to bind to a single eventfd, even across VMs.
Signed-off-by: Sean Christopherson seanjc@google.com --- tools/testing/selftests/kvm/Makefile.kvm | 1 + tools/testing/selftests/kvm/irqfd_test.c | 130 +++++++++++++++++++++++ 2 files changed, 131 insertions(+) create mode 100644 tools/testing/selftests/kvm/irqfd_test.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm index f62b0a5aba35..318adf3ef6b6 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -54,6 +54,7 @@ TEST_PROGS_x86 += x86/nx_huge_pages_test.sh TEST_GEN_PROGS_COMMON = demand_paging_test TEST_GEN_PROGS_COMMON += dirty_log_test TEST_GEN_PROGS_COMMON += guest_print_test +TEST_GEN_PROGS_COMMON += irqfd_test TEST_GEN_PROGS_COMMON += kvm_binary_stats_test TEST_GEN_PROGS_COMMON += kvm_create_max_vcpus TEST_GEN_PROGS_COMMON += kvm_page_table_test diff --git a/tools/testing/selftests/kvm/irqfd_test.c b/tools/testing/selftests/kvm/irqfd_test.c new file mode 100644 index 000000000000..286f2b15fde6 --- /dev/null +++ b/tools/testing/selftests/kvm/irqfd_test.c @@ -0,0 +1,130 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <errno.h> +#include <pthread.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <signal.h> +#include <stdint.h> +#include <sys/sysinfo.h> + +#include "kvm_util.h" + +static struct kvm_vm *vm1; +static struct kvm_vm *vm2; +static int __eventfd; +static bool done; + +/* + * KVM de-assigns based on eventfd *and* GSI, but requires unique eventfds when + * assigning (the API isn't symmetrical). Abuse the oddity and use a per-task + * GSI base to avoid false failures due to cross-task de-assign, i.e. so that + * the secondary doesn't de-assign the primary's eventfd and cause assign to + * unexpectedly succeed on the primary. + */ +#define GSI_BASE_PRIMARY 0x20 +#define GSI_BASE_SECONDARY 0x30 + +static void juggle_eventfd_secondary(struct kvm_vm *vm, int eventfd) +{ + int r, i; + + /* + * The secondary task can encounter EBADF since the primary can close + * the eventfd at any time. And because the primary can recreate the + * eventfd, at the safe fd in the file table, the secondary can also + * encounter "unexpected" success, e.g. if the close+recreate happens + * between the first and second assignments. The secondary's role is + * mostly to antagonize KVM, not to detect bugs. + */ + for (i = 0; i < 2; i++) { + r = __kvm_irqfd(vm, GSI_BASE_SECONDARY, eventfd, 0); + TEST_ASSERT(!r || errno == EBUSY || errno == EBADF, + "Wanted success, EBUSY, or EBADF, r = %d, errno = %d", + r, errno); + + /* De-assign should succeed unless the eventfd was closed. */ + r = __kvm_irqfd(vm, GSI_BASE_SECONDARY + i, eventfd, KVM_IRQFD_FLAG_DEASSIGN); + TEST_ASSERT(!r || errno == EBADF, + "De-assign should succeed unless the fd was closed"); + } +} + +static void *secondary_irqfd_juggler(void *ign) +{ + while (!READ_ONCE(done)) { + juggle_eventfd_secondary(vm1, READ_ONCE(__eventfd)); + juggle_eventfd_secondary(vm2, READ_ONCE(__eventfd)); + } + + return NULL; +} + +static void juggle_eventfd_primary(struct kvm_vm *vm, int eventfd) +{ + int r1, r2; + + /* + * At least one of the assigns should fail. KVM disallows assigning a + * single eventfd to multiple GSIs (or VMs), so it's possible that both + * assignments can fail, too. + */ + r1 = __kvm_irqfd(vm, GSI_BASE_PRIMARY, eventfd, 0); + TEST_ASSERT(!r1 || errno == EBUSY, + "Wanted success or EBUSY, r = %d, errno = %d", r1, errno); + + r2 = __kvm_irqfd(vm, GSI_BASE_PRIMARY + 1, eventfd, 0); + TEST_ASSERT(r1 || (r2 && errno == EBUSY), + "Wanted failure (EBUSY), r1 = %d, r2 = %d, errno = %d", + r1, r2, errno); + + /* + * De-assign should always succeed, even if the corresponding assign + * failed. + */ + kvm_irqfd(vm, GSI_BASE_PRIMARY, eventfd, KVM_IRQFD_FLAG_DEASSIGN); + kvm_irqfd(vm, GSI_BASE_PRIMARY + 1, eventfd, KVM_IRQFD_FLAG_DEASSIGN); +} + +int main(int argc, char *argv[]) +{ + pthread_t racing_thread; + int r, i; + + /* Create "full" VMs, as KVM_IRQFD requires an in-kernel IRQ chip. */ + vm1 = vm_create(1); + vm2 = vm_create(1); + + WRITE_ONCE(__eventfd, kvm_new_eventfd()); + + kvm_irqfd(vm1, 10, __eventfd, 0); + + r = __kvm_irqfd(vm1, 11, __eventfd, 0); + TEST_ASSERT(r && errno == EBUSY, + "Wanted EBUSY, r = %d, errno = %d", r, errno); + + r = __kvm_irqfd(vm2, 12, __eventfd, 0); + TEST_ASSERT(r && errno == EBUSY, + "Wanted EBUSY, r = %d, errno = %d", r, errno); + + kvm_irqfd(vm1, 11, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN); + kvm_irqfd(vm1, 12, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN); + kvm_irqfd(vm1, 13, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN); + kvm_irqfd(vm1, 14, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN); + kvm_irqfd(vm1, 10, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN); + + close(__eventfd); + + pthread_create(&racing_thread, NULL, secondary_irqfd_juggler, vm2); + + for (i = 0; i < 10000; i++) { + WRITE_ONCE(__eventfd, kvm_new_eventfd()); + + juggle_eventfd_primary(vm1, __eventfd); + juggle_eventfd_primary(vm2, __eventfd); + close(__eventfd); + } + + WRITE_ONCE(done, true); + pthread_join(racing_thread, NULL); +}