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SubjectRe: [PATCH MANUALSEL 5.10 3/4] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
From
On 12/13/21 15:20, Sasha Levin wrote:
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> [ Upstream commit 908fa88e420f30dde6d80f092795a18ec72ca6d3 ]
>
> 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@redhat.com>
> Message-Id: <20211123135953.667434-1-vkuznets@redhat.com>
> [Skip the test if the hard limit can be raised. - Paolo]
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> Tested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> .../selftests/kvm/kvm_create_max_vcpus.c | 30 +++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
> index 0299cd81b8ba2..aa3795cd7bd3d 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 +41,39 @@ 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) {
> + int old_rlim_max = rl.rlim_max;
> + rl.rlim_max = nr_fds_wanted;
> +
> + int r = setrlimit(RLIMIT_NOFILE, &rl);
> + if (r < 0) {
> + printf("RLIMIT_NOFILE hard limit is too low (%d, wanted %d)\n",
> + old_rlim_max, nr_fds_wanted);
> + exit(KSFT_SKIP);
> + }
> + } else {
> + TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
> + }
> + }
> +
> /*
> * Upstream KVM prior to 4.8 does not support KVM_CAP_MAX_VCPU_ID.
> * Userspace is supposed to use KVM_CAP_MAX_VCPUS as the maximum ID
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

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