On Thu, Mar 24, 2022 at 05:19:34PM +0000, Sean Christopherson wrote:
> On Tue, Mar 22, 2022, Ricardo Koller wrote:
> > Add is_cpu_online() utility function: a wrapper for
> > "/sys/devices/system/cpu/cpu%d/online".
> >
> > Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
> > ---
> > tools/testing/selftests/kvm/include/test_util.h | 2 ++
> > tools/testing/selftests/kvm/lib/test_util.c | 16 ++++++++++++++++
> > 2 files changed, 18 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> > index 99e0dcdc923f..14084dc4e152 100644
> > --- a/tools/testing/selftests/kvm/include/test_util.h
> > +++ b/tools/testing/selftests/kvm/include/test_util.h
> > @@ -143,4 +143,6 @@ static inline void *align_ptr_up(void *x, size_t size)
> > return (void *)align_up((unsigned long)x, size);
> > }
> >
> > +bool is_cpu_online(int pcpu);
> > +
> > #endif /* SELFTEST_KVM_TEST_UTIL_H */
> > diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> > index 6d23878bbfe1..81950e6b6d10 100644
> > --- a/tools/testing/selftests/kvm/lib/test_util.c
> > +++ b/tools/testing/selftests/kvm/lib/test_util.c
> > @@ -334,3 +334,19 @@ long get_run_delay(void)
> >
> > return val[1];
> > }
> > +
> > +bool is_cpu_online(int pcpu)
> > +{
> > + char p[128];
> > + FILE *fp;
> > + int ret;
> > +
> > + snprintf(p, sizeof(p), "/sys/devices/system/cpu/cpu%d/online", pcpu);
>
> I don't think this is sufficient for the use in patch 03; the CPU could be online
> but disallowed for use by the current task. I think what you want instead is a
> combination of get_nprocs_conf() + sched_getaffinity() + CPU_ISSET().
Good point. I was just thinking about the more common situation where a
user tries to use a CPU that doesn't even exist. Will fix in v4.
Thanks,
Ricardo
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