Re: [Xen-devel] [PATCH v7 2/6] domain: introduce XEN_DOMCTL_CDF_iommu flag

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.08.2019 10:29, Paul Durrant wrote:
> This patch introduces a common domain creation flag to determine whether
> the domain is permitted to make use of the IOMMU. Currently the flag is
> always set (for both dom0 and domU) if the IOMMU is globally enabled
> (i.e. iommu_enabled == 1). sanitise_domain_config() is modified to reject
> the flag if !iommu_enabled.
> 
> A new helper function, is_iommu_enabled(), is added to test the flag and
> iommu_domain_init() will return immediately if !is_iommu_enabled(). This is
> slightly different to the previous behaviour based on !iommu_enabled where
> the call to arch_iommu_domain_init() was made regardless, however it appears
> that this call was only necessary to initialize the dt_devices list for ARM
> such that iommu_release_dt_devices() can be called unconditionally by
> domain_relinquish_resources(). Adding a simple check of is_iommu_enabled()
> into iommu_release_dt_devices() keeps this unconditional call working.
> 
> No functional change should be observed with this patch applied.
> 
> Subsequent patches will allow the toolstack to control whether use of the
> IOMMU is enabled for a domain.
> 
> NOTE: The introduction of the is_iommu_enabled() helper function might
>       seem excessive but its use is expected to increase with subsequent
>       patches. Also, having iommu_domain_init() bail before calling
>       arch_iommu_domain_init() is not strictly necessary, but I think the
>       consequent addition of the call to is_iommu_enabled() in
>       iommu_release_dt_devices() makes the code clearer.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Reviewed-by: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>

Hypervisor parts (non-Arm)
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan

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