Re: [Xen-devel] [PATCH v14 9/9] mm / iommu: split need_iommu() into has_iommu_pt() and need_iommu_pt_sync()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.10.18 at 12:45, <paul.durrant@xxxxxxxxxx> wrote:
> The name 'need_iommu()' is a little confusing as it suggests a domain needs
> to use the IOMMU but something might not be set up yet, when in fact it
> represents a tri-state value (not a boolean as might be expected) where
> -1 means 'IOMMU mappings being set up' and 1 means 'IOMMU mappings have
> been fully set up'.
> 
> Two different meanings are also inferred from the macro it in various
> places in the code:
> 
> - Some callers want to test whether a domain has IOMMU mappings at all
> - Some callers want to test whether they need to synchronize the domain's
>   P2M and IOMMU mappings
> 
> This patch replaces the 'need_iommu' tri-state value with a defined
> enumeration and adds a boolean flag 'need_sync' to separate these meanings,
> and places both of these in struct domain_iommu, rather than directly in
> struct domain.
> This patch also creates two new boolean macros:
> 
> - 'has_iommu_pt()' evaluates to true if a domain has IOMMU mappings, even
>   if they are still under construction.
> - 'need_iommu_pt_sync()' evaluates to true if a domain requires explicit
>   synchronization of the P2M and IOMMU mappings.
> 
> All callers of need_iommu() are then modified to use the macro appropriate
> to what they are trying to test, except for the instance in
> xen/drivers/passthrough/pci.c:assign_device() which has simply been
> removed since it appears to be unnecessary.
> 
> NOTE: There are some callers of need_iommu() that strictly operate on
>       the hardware domain. In some of these case a more global flag is
>       used instead.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

Except for the Arm parts
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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