Re: [Xen-devel] [PATCH v6 2/7] VMX: Properly handle pi when all the assigned devices are removed

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.10.16 at 04:37, <feng.wu@xxxxxxxxx> wrote:
> @@ -215,11 +220,21 @@ void vmx_pi_hooks_assign(struct domain *d)
>  /* This function is called when pcidevs_lock is held */
>  void vmx_pi_hooks_deassign(struct domain *d)
>  {
> +    struct vcpu *v;
> +
>      if ( !iommu_intpost || !has_hvm_container_domain(d) )
>          return;
>  
>      ASSERT(d->arch.hvm_domain.vmx.vcpu_block);
>  
> +    /*
> +     * Pausing the domain can make sure the vCPU is not
> +     * running and hence not calling the hooks simultaneously
> +     * when deassigning the PI hooks and removing the vCPU
> +     * from the blocking list.
> +     */
> +    domain_pause(d);

There's one additional caveat here which no-one of us so far thought
of: Currently there's nothing preventing the domctl-s under which
this sits from being issued by the control domain for itself. Various
other domctl-s, however, guard against this case when intending
to pause the target domain. The same needs to be done for the
ones leading here.

Jan

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