Re: [Xen-devel] [PATCH v3 12/12] xen/domain: Allocate d->vcpu[] in domain_create()

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andrew,

On 08/29/2018 03:40 PM, Andrew Cooper wrote:
> For ARM, the call to arch_domain_create() needs to have completed before
> domain_max_vcpus() will return the correct upper bound.
>
> For each arch's dom0's, drop the temporary max_vcpus parameter, and allocation
> of dom0->vcpu.
>
> With d->max_vcpus now correctly configured before evtchn_init(), the poll mask
> can be constructed suitably for the domain, rather than for the worst-case
> setting.
>
> Due to the evtchn_init() fixes, it no longer calls domain_max_vcpus(), and
> ARM's two implementations of vgic_max_vcpus() no longer need work around the
> out-of-order call.
>
>  From this point on, d->max_vcpus and d->vcpus[] are valid for any domain which
> can be looked up by domid.
>
> The XEN_DOMCTL_max_vcpus hypercall is modified to reject any call attempt with
> max != d->max_vcpus, which does match the older semantics (not that it is
> obvious from the code).  The logic to allocate d->vcpu[] is dropped, but at
> this point the hypercall still needs making to allocate each vcpu.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
With one request below, for the ARM + Common code:

Acked-by: Julien Grall <julien.grall@xxxxxxx>

FAOD, I agree with your position to avoid the renaming.

[...]

> diff --git a/xen/common/domctl.c b/xen/common/domctl.c
> index 58e51b2..8a803b3 100644
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -547,6 +547,13 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
> u_domctl)
>           break;
>       }
>   
> +    /*
> +     * Note: The parameter passed to XEN_DOMCTL_max_vcpus must match the value
> +     * passed to XEN_DOMCTL_createdomain.  This hypercall is in the process of
> +     * being removed (once the failure paths in domain_create() have been
> +     * improved), but is still required in the short term to allocate the
> +     * vcpus themselves.
> +     */
This comment might be more useful in the public header. This is usually 
the first place I would look for description of a domctl.
Cheers,

--
Julien Grall

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