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

Hi Paul,

On 04/10/2018 11:45, Paul Durrant 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>

For the Arm bits:

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


Julien Grall

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