Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-11 Thread Jan Beulich
>>> On 03.04.19 at 12:17, wrote: > On 03/04/2019 10:33, Jan Beulich wrote: > On 02.04.19 at 21:57, wrote: >>> +if ( x86_cpu_to_apicid[cpu] & sibling_mask ) >>> +ret = cpu_up_helper(_p(cpu)); >> Shouldn't this be restricted to CPUs a sibling of which is already >> online? A

Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-03 Thread Jan Beulich
>>> On 03.04.19 at 13:33, wrote: > On 03/04/2019 11:44, Jan Beulich wrote: > On 03.04.19 at 12:17, wrote: >>> On 03/04/2019 10:33, Jan Beulich wrote: >>> On 02.04.19 at 21:57, wrote: > Slightly RFC. I'm not very happy with the contination situation, but > -EBUSY > is the pr

Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-03 Thread Andrew Cooper
On 03/04/2019 11:44, Jan Beulich wrote: On 03.04.19 at 12:17, wrote: >> On 03/04/2019 10:33, Jan Beulich wrote: >> On 02.04.19 at 21:57, wrote: Slightly RFC. I'm not very happy with the contination situation, but -EBUSY is the preexisting style and it seems like it is th

Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-03 Thread Jan Beulich
>>> On 03.04.19 at 12:17, wrote: > On 03/04/2019 10:33, Jan Beulich wrote: > On 02.04.19 at 21:57, wrote: >>> Slightly RFC. I'm not very happy with the contination situation, but -EBUSY >>> is the preexisting style and it seems like it is the only option from >>> tasklet >>> context. >> Wel

Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-03 Thread Andrew Cooper
On 03/04/2019 10:33, Jan Beulich wrote: On 02.04.19 at 21:57, wrote: >> Currently, a user can in combine the output of `xl info -n`, the APCI tables, >> and some manual CPUID data to figure out which CPU numbers to feed into >> `xen-hptool cpu-offline` to effectively disable SMT at runtime. >

Re: [Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-03 Thread Jan Beulich
>>> On 02.04.19 at 21:57, wrote: > Currently, a user can in combine the output of `xl info -n`, the APCI tables, > and some manual CPUID data to figure out which CPU numbers to feed into > `xen-hptool cpu-offline` to effectively disable SMT at runtime. > > A more convenient option is to teach Xen

[Xen-devel] [PATCH 3/3] x86/smt: Support for enabling/disabling SMT at runtime

2019-04-02 Thread Andrew Cooper
Currently, a user can in combine the output of `xl info -n`, the APCI tables, and some manual CPUID data to figure out which CPU numbers to feed into `xen-hptool cpu-offline` to effectively disable SMT at runtime. A more convenient option is to teach Xen how to perform this action. First of all,