Re: [Xen-devel] [PATCH 3/6] xen/pvshim: identity pin shim vCPUs to pCPUs

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jan 17, 2018 at 09:48:11AM +0000, Roger Pau Monne wrote:
> Since VCPUOP_{up/down} already identity pins vCPU hotplug to pCPU
> hotplug also pin the vCPUs to the pCPUs in the scheduler. This prevent

The description is a bit ambiguous. I read it as "the shim hotplug code
pins vcpu to pcpu while doing VCPUOP_{up/down}" but in fact it is "the
shim hotplug code assumes identity mapping between vcpu and pcpu".

With this clarified.

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

> vCPU migration and should improve performance.
> 
> While there also use __cpumask_set_cpu instead of cpumask_set_cpu,
> there's no need to use the locked variant.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> ---
> Should be backported to the 4.10.0-shim-comet branch.
> ---
>  xen/arch/x86/dom0_build.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
> index 17cb1272c1..555660b853 100644
> --- a/xen/arch/x86/dom0_build.c
> +++ b/xen/arch/x86/dom0_build.c
> @@ -140,9 +140,8 @@ struct vcpu *__init dom0_setup_vcpu(struct domain *d,
>      {
>          if ( pv_shim )
>          {
> -
> -            cpumask_setall(v->cpu_hard_affinity);
> -            cpumask_setall(v->cpu_soft_affinity);
> +            __cpumask_set_cpu(vcpu_id, v->cpu_hard_affinity);
> +            __cpumask_set_cpu(vcpu_id, v->cpu_soft_affinity);
>          }
>          else
>          {
> -- 
> 2.15.1
> 

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