* [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
@ 2021-11-23 13:59 Vitaly Kuznetsov
2021-11-24 18:50 ` Sean Christopherson
0 siblings, 1 reply; 3+ messages in thread
From: Vitaly Kuznetsov @ 2021-11-23 13:59 UTC (permalink / raw)
To: kvm, Paolo Bonzini
Cc: Sean Christopherson, Wanpeng Li, Jim Mattson, linux-kernel
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>
---
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;
+
+ 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
--
2.33.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-11-23 13:59 [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Vitaly Kuznetsov
@ 2021-11-24 18:50 ` Sean Christopherson
2021-11-26 12:32 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Sean Christopherson @ 2021-11-24 18:50 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-kernel
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@redhat.com>
> ---
> 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@google.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-11-24 18:50 ` Sean Christopherson
@ 2021-11-26 12:32 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2021-11-26 12:32 UTC (permalink / raw)
To: Sean Christopherson, Vitaly Kuznetsov
Cc: kvm, Wanpeng Li, Jim Mattson, linux-kernel
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@google.com>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-11-23 13:59 [PATCH v2] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Vitaly Kuznetsov
2021-11-24 18:50 ` Sean Christopherson
2021-11-26 12:32 ` Paolo Bonzini
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