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

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>
This commit is contained in:
Vitaly Kuznetsov 2021-11-23 14:59:53 +01:00 committed by Paolo Bonzini
parent feb627e8d6
commit 908fa88e42
1 changed files with 30 additions and 0 deletions
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30
tools/testing/selftests/kvm/kvm_create_max_vcpus.c
View File

@ -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