RE: [PATCH v2 08/10] remove remaining uses of iommu_legacy_map/unmap

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Paul Durrant <paul@xxxxxxx>
> Sent: 30 July 2020 15:29
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Durrant, Paul <pdurrant@xxxxxxxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; 
> Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Roger Pau Monné 
> <roger.pau@xxxxxxxxxx>; George
> Dunlap <george.dunlap@xxxxxxxxxx>; Ian Jackson <ian.jackson@xxxxxxxxxxxxx>; 
> Julien Grall
> <julien@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>; Jun Nakajima 
> <jun.nakajima@xxxxxxxxx>;
> Kevin Tian <kevin.tian@xxxxxxxxx>
> Subject: [EXTERNAL] [PATCH v2 08/10] remove remaining uses of 
> iommu_legacy_map/unmap
> 
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> From: Paul Durrant <pdurrant@xxxxxxxxxx>
> 
> The 'legacy' functions do implicit flushing so amend the callers to do the
> appropriate flushing.
> 
> Unfortunately, because of the structure of the P2M code, we cannot remove
> the per-CPU 'iommu_dont_flush_iotlb' global and the optimization it
> facilitates. It is now checked directly iommu_iotlb_flush(). Also, it is
> now declared as bool (rather than bool_t) and setting/clearing it are no
> longer pointlessly gated on is_iommu_enabled() returning true. (Arguably
> it is also pointless to gate the call to iommu_iotlb_flush() on that
> condition - since it is a no-op in that case - but the if clause allows
> the scope of a stack variable to be restricted).
> 
> NOTE: The code in memory_add() now fails if the number of pages passed to
>       a single call overflows an unsigned int. I don't believe this will
>       ever happen in practice.
> 
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>

I realise now that I completely forgot to address Jan's comments on grant table 
locking and flush batching, so there will be a v3 of at least this patch.

  Paul