* [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
@ 2021-11-22 17:19 Vitaly Kuznetsov
2021-11-22 17:38 ` Sean Christopherson
0 siblings, 1 reply; 4+ messages in thread
From: Vitaly Kuznetsov @ 2021-11-22 17:19 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>
---
.../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..19198477a10e 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"
@@ -19,6 +20,9 @@
#include "asm/kvm.h"
#include "linux/kvm.h"
+/* 'Safe' number of open file descriptors in addition to vCPU fds needed */
+#define NOFD 16
+
void test_vcpu_creation(int first_vcpu_id, int num_vcpus)
{
struct kvm_vm *vm;
@@ -40,10 +44,28 @@ 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);
+ 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);
+ /*
+ * Creating KVM_CAP_MAX_VCPUS vCPUs require KVM_CAP_MAX_VCPUS open
+ * file decriptors.
+ */
+ TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl),
+ "getrlimit() failed (errno: %d)", errno);
+
+ if (kvm_max_vcpus > rl.rlim_cur - NOFD) {
+ rl.rlim_cur = kvm_max_vcpus + NOFD;
+
+ if (kvm_max_vcpus > rl.rlim_max - NOFD)
+ rl.rlim_max = kvm_max_vcpus + NOFD;
+
+ TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl),
+ "setrlimit() failed (errno: %d)", errno);
+ }
+
/*
* 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] 4+ messages in thread
* Re: [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-11-22 17:19 [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Vitaly Kuznetsov
@ 2021-11-22 17:38 ` Sean Christopherson
2021-11-22 18:03 ` Vitaly Kuznetsov
0 siblings, 1 reply; 4+ messages in thread
From: Sean Christopherson @ 2021-11-22 17:38 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-kernel
On Mon, Nov 22, 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>
> ---
> .../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..19198477a10e 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"
>
> @@ -19,6 +20,9 @@
> #include "asm/kvm.h"
> #include "linux/kvm.h"
>
> +/* 'Safe' number of open file descriptors in addition to vCPU fds needed */
> +#define NOFD 16
Any reason not to make this "buffer" extra large, e.g. 100+ to avoid having to
debug this issue again in the future?
> +
> void test_vcpu_creation(int first_vcpu_id, int num_vcpus)
> {
> struct kvm_vm *vm;
> @@ -40,10 +44,28 @@ 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);
Rather than a separate define that's hard to describe succintly, what about:
int nr_fds_wanted = kvm_max_vcpus + <arbitrary number>
and then the body becomes
if (nr_fds_wanted > rl.rlim_cur) {
rl.rlim_cur = nr_fds_wanted;
rl.rlim_max = max(rl.rlim_max, nr_fds_wanted);
...
}
> + 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);
>
> + /*
> + * Creating KVM_CAP_MAX_VCPUS vCPUs require KVM_CAP_MAX_VCPUS open
> + * file decriptors.
> + */
> + TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl),
> + "getrlimit() failed (errno: %d)", errno);
And strerror() output too?
> +
> + if (kvm_max_vcpus > rl.rlim_cur - NOFD) {
> + rl.rlim_cur = kvm_max_vcpus + NOFD;
> +
> + if (kvm_max_vcpus > rl.rlim_max - NOFD)
> + rl.rlim_max = kvm_max_vcpus + NOFD;
> +
> + TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl),
> + "setrlimit() failed (errno: %d)", errno);
> + }
> +
> /*
> * 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 [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-11-22 17:38 ` Sean Christopherson
@ 2021-11-22 18:03 ` Vitaly Kuznetsov
2021-11-23 13:52 ` Vitaly Kuznetsov
0 siblings, 1 reply; 4+ messages in thread
From: Vitaly Kuznetsov @ 2021-11-22 18:03 UTC (permalink / raw)
To: Sean Christopherson
Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-kernel
Sean Christopherson <seanjc@google.com> writes:
> On Mon, Nov 22, 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>
>> ---
>> .../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..19198477a10e 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"
>>
>> @@ -19,6 +20,9 @@
>> #include "asm/kvm.h"
>> #include "linux/kvm.h"
>>
>> +/* 'Safe' number of open file descriptors in addition to vCPU fds needed */
>> +#define NOFD 16
>
> Any reason not to make this "buffer" extra large, e.g. 100+ to avoid having to
> debug this issue again in the future?
>
No, not really. We could've avoided this ambiguity completely by
checking how many fds are already open but all methods I can think of
are 'too much'. In my testing I needed around 10 so I put '16' but '100'
is even better.
>> +
>> void test_vcpu_creation(int first_vcpu_id, int num_vcpus)
>> {
>> struct kvm_vm *vm;
>> @@ -40,10 +44,28 @@ 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);
>
> Rather than a separate define that's hard to describe succintly, what about:
>
> int nr_fds_wanted = kvm_max_vcpus + <arbitrary number>
>
> and then the body becomes
>
> if (nr_fds_wanted > rl.rlim_cur) {
> rl.rlim_cur = nr_fds_wanted;
> rl.rlim_max = max(rl.rlim_max, nr_fds_wanted);
>
> ...
> }
Sure but a "succinct" comment will still be needed, either near the
'NOFD' define or above 'int nr_fds_wanted' :-)
>
>> + 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);
>>
>> + /*
>> + * Creating KVM_CAP_MAX_VCPUS vCPUs require KVM_CAP_MAX_VCPUS open
>> + * file decriptors.
>> + */
>> + TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl),
>> + "getrlimit() failed (errno: %d)", errno);
>
> And strerror() output too?
>
Sure, will add in v2.
>> +
>> + if (kvm_max_vcpus > rl.rlim_cur - NOFD) {
>> + rl.rlim_cur = kvm_max_vcpus + NOFD;
>> +
>> + if (kvm_max_vcpus > rl.rlim_max - NOFD)
>> + rl.rlim_max = kvm_max_vcpus + NOFD;
>> +
>> + TEST_ASSERT(!setrlimit(RLIMIT_NOFILE, &rl),
>> + "setrlimit() failed (errno: %d)", errno);
>> + }
>> +
>> /*
>> * 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
>>
>
--
Vitaly
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE
2021-11-22 18:03 ` Vitaly Kuznetsov
@ 2021-11-23 13:52 ` Vitaly Kuznetsov
0 siblings, 0 replies; 4+ messages in thread
From: Vitaly Kuznetsov @ 2021-11-23 13:52 UTC (permalink / raw)
To: Sean Christopherson
Cc: kvm, Paolo Bonzini, Wanpeng Li, Jim Mattson, linux-kernel
Vitaly Kuznetsov <vkuznets@redhat.com> writes:
>>>
>>> + /*
>>> + * Creating KVM_CAP_MAX_VCPUS vCPUs require KVM_CAP_MAX_VCPUS open
>>> + * file decriptors.
>>> + */
>>> + TEST_ASSERT(!getrlimit(RLIMIT_NOFILE, &rl),
>>> + "getrlimit() failed (errno: %d)", errno);
>>
>> And strerror() output too?
>>
>
> Sure, will add in v2.
>
Actually, there are two issues with the code above. First, TEST_ASSERT()
already prints both errno and strerror() (setrlimit() counterpart which
is easier to make fail):
KVM_CAP_MAX_VCPU_ID: 4096
KVM_CAP_MAX_VCPUS: 1024
==== Test Assertion Failure ====
kvm_create_max_vcpus.c:68: !setrlimit(RLIMIT_NOFILE, &rl)
pid=344504 tid=344504 errno=1 - Operation not permitted
1 0x0000000000402485: main at kvm_create_max_vcpus.c:68
2 0x00007fcb2e8b4041: ?? ??:0
3 0x000000000040254d: _start at ??:?
setrlimit() failed, errno: 0
Second, note "errno: 0" above. There's no guarantee that getrlimit()
will be executed before evaluating 'errno' in C. I think I'll just drop
redundant errno printout then.
--
Vitaly
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-11-23 13:52 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-11-22 17:19 [PATCH] KVM: selftests: Make sure kvm_create_max_vcpus test won't hit RLIMIT_NOFILE Vitaly Kuznetsov
2021-11-22 17:38 ` Sean Christopherson
2021-11-22 18:03 ` Vitaly Kuznetsov
2021-11-23 13:52 ` Vitaly Kuznetsov
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).