On 28/05/2019 13:44, Jan Beulich wrote:
>>>> On 28.05.19 at 12:33, <jgr...@suse.com> wrote:
>> --- a/xen/arch/x86/sysctl.c
>> +++ b/xen/arch/x86/sysctl.c
>> @@ -200,7 +200,8 @@ long arch_do_sysctl(
>>
>> case XEN_SYSCTL_CPU_HOTPLUG_SMT_ENABLE:
>> case XEN_SYSCTL_CPU_HOTPLUG_SMT_DISABLE:
>> - if ( !cpu_has_htt || boot_cpu_data.x86_num_siblings < 2 )
>> + if ( !cpu_has_htt || boot_cpu_data.x86_num_siblings < 2 ||
>> + sched_disable_smt_switching )
>> {
>> ret = -EOPNOTSUPP;
>> break;
>
> I'm not convinced -EOPNOTSUPP is an appropriate error code for
> this new case. -EPERM, -EACCES, or -EIO would all seem more
> appropriate to me (and perhaps there are further ones).
I think -EIO or -EBUSY would be the best fit.
>
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -57,6 +57,7 @@ integer_param("sched_ratelimit_us", sched_ratelimit_us);
>>
>> /* Number of vcpus per struct sched_unit. */
>> static unsigned int sched_granularity = 1;
>> +bool sched_disable_smt_switching;
>
> __read_mostly (perhaps also the pre-existing variable in context)?
Yes, can do.
Juergen
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