KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE

BugLink: https://bugs.launchpad.net/bugs/1957991
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
index 231d79e57774e6e3633e7bd2792158ce9f2eac19..cfe75536d8a5597a4669953bc9c39df5915f4df8 100644 (file)
--- 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"
 
@@ -43,10 +44,39 @@ 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;
 
        printf("KVM_CAP_MAX_VCPU_ID: %d\n", kvm_max_vcpu_id);
        printf("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