On Tue, Nov 23, 2021, Vitaly Kuznetsov wrote:
> With the elevated 'KVM_CAP_MAX_VCPUS' value kvm_create_max_vcpus test
> may hit RLIMIT_NOFILE limits:
>
> # ./kvm_create_max_vcpus
> KVM_CAP_MAX_VCPU_ID: 4096
> KVM_CAP_MAX_VCPUS: 1024
> Testing creating 1024 vCPUs, with IDs 0...1023.
> /dev/kvm not available (errno: 24), skipping test
>
> Adjust RLIMIT_NOFILE limits to make sure KVM_CAP_MAX_VCPUS fds can be
> opened. Note, raising hard limit ('rlim_max') requires CAP_SYS_RESOURCE
> capability which is generally not needed to run kvm selftests (but without
> raising the limit the test is doomed to fail anyway).
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> Changes since v1:
> - Drop 'NOFD' define replacing it with 'int nr_fds_wanted' [Sean]
> - Drop 'errno' printout as TEST_ASSERT() already does that.
> ---
> .../selftests/kvm/kvm_create_max_vcpus.c | 22 +++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> index f968dfd4ee88..ca957fe3f903 100644
> --- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> +++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> @@ -12,6 +12,7 @@
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> +#include <sys/resource.h>
>
> #include "test_util.h"
>
> @@ -40,10 +41,31 @@ int main(int argc, char *argv[])
> {
> int kvm_max_vcpu_id = kvm_check_cap(KVM_CAP_MAX_VCPU_ID);
> int kvm_max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
> + /*
> + * Number of file descriptors reqired, KVM_CAP_MAX_VCPUS for vCPU fds +
> + * an arbitrary number for everything else.
> + */
> + int nr_fds_wanted = kvm_max_vcpus + 100;
> + struct rlimit rl;
>
> pr_info("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
> pr_info("KVM_CAP_MAX_VCPUS: %d\n", kvm_max_vcpus);
>
> + /*
> + * Check that we're allowed to open nr_fds_wanted file descriptors and
> + * try raising the limits if needed.
> + */
> + TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl), "getrlimit() failed!");
> +
> + if (rl.rlim_cur < nr_fds_wanted) {
> + rl.rlim_cur = nr_fds_wanted;
> +
> + if (rl.rlim_max < nr_fds_wanted)
> + rl.rlim_max = nr_fds_wanted;
Nit, this could use max().
Reviewed-and-tested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
