Re: [Xen-devel] [PATCH v2] x86/smt: Support for enabling/disabling SMT at runtime

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Apr 08, 2019 at 06:02:19PM +0100, Andrew Cooper 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 how to perform this action.
> 
> Extend XEN_SYSCTL_cpu_hotplug with two new operations.  Introduce a new
> smt_up_down_helper() which wrap the cpu_{up,down}_helper() helpers with logic
> which understands siblings based on their APIC_ID.
> 
> Add libxc stubs, and extend xen-hptool with smt-{enable,disable} options.
> These are intended to be shorthands for a loop over cpu-{online,offline}.  It
> is intended for use in production scenarios where debugging options such as
> `maxcpus=` or other manual plug/unplug configuration has not been used.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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