linux-kernel - Re: [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT

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Message-ID: <54225ff0-b90a-6c1f-f474-2338df21befa@redhat.com>
Date:   Fri, 26 Nov 2021 13:32:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test
 won't hit RLIMIT_NOFILE

On 11/24/21 19:50, Sean Christopherson wrote:
>> +	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().

If the hard limit is too low, the right thing to do is to skip the test:

--- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
+++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
@@ -59,11 +59,19 @@ int main(int argc, char *argv[])
  
  	if (rl.rlim_cur < nr_fds_wanted) {
  		rl.rlim_cur = nr_fds_wanted;
-
-		if (rl.rlim_max <  nr_fds_wanted)
+		if (rl.rlim_max < nr_fds_wanted) {
+			int old_rlim_max = rl.rlim_max;
  			rl.rlim_max = nr_fds_wanted;
  
-		TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl), "setrlimit() failed!");
+			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!");
+		}
  	}
  
  	/*

Nevertheless, thanks for the fix and the review! (I might have missed it
if it wasn't for your remark).

Paolo
> Reviewed-and-tested-by: Sean Christopherson<seanjc@...gle.com>  
>