Re: [Xen-devel] [PATCH RFC 31/49] xen/sched: use sched_resource cpu instead smp_processor_id in schedulers

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.03.19 at 11:22, <jgross@xxxxxxxx> wrote:
> On 29/03/2019 20:36, Andrew Cooper wrote:
>> In practice, all this flag does is permit the use of VCPUOP_get_physid,
>> disallow the use of vcpu_set_hard_affinity(), and allow dom0 to attempt
>> to actually write to MSR_AMD64_NB_CFG, MSR_FAM10H_MMIO_CONF_BASE,
>> MSR_IA32_UCODE_REV, MSR_IA32_THERM_CONTROL and
>> MSR_IA32_ENERGY_PERF_BIAS, rather than having the write silently discarded.
>> 
>> Dom0's use of those MSRs is dubious at best, and disabled by default,
>> *and* when active, also cross-checks with the hard affinity mask.  Does
>> anyone use dom0_vcpus_pin in production?
> 
> I have seen it on customer systems.

Same here, but I've never seen it used for a good reason.

>> I think there is quite a lot of value in getting rid of d->is_pinned and
>> is_pinned_vcpu() entirely, with will remove an extreme
>> corner-case-x86-ism out of the common code.

I think its origin was "cpufreq=dom0-kernel", which I think should go
away with it then.

Jan



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