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Date: Tue, 2 May 2017 18:25:50 +0200
From: Cornelia Huck <cornelia.huck@de.ibm.com>
In-Reply-To: <20170429123707.16675-1-aik@ozlabs.ru>
References: <20170429123707.16675-1-aik@ozlabs.ru>
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Subject: Re: [Qemu-devel] [PATCH qemu v5] memory/iommu: QOM'fy IOMMU
 MemoryRegion
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To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, David Gibson <david@gibson.dropbear.id.au>, Alex Williamson <alex.williamson@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>, Philippe =?UTF-8?B?TWF0aGlldS1EYXVkw6k=?= <f4bug@amsat.org>

On Sat, 29 Apr 2017 22:37:07 +1000
Alexey Kardashevskiy <aik@ozlabs.ru> wrote:

> This defines new QOM object - IOMMUMemoryRegion - with MemoryRegion
> as a parent.
> 
> This moves IOMMU-related fields from MR to IOMMU MR. However to avoid
> dymanic QOM casting in fast path (address_space_translate, etc),
> this adds an @is_iommu boolean flag to MR and provides new helper to
> do simple cast to IOMMU MR - memory_region_get_iommu. The flag
> is set in the instance init callback. This defines
> memory_region_is_iommu as memory_region_get_iommu()!=NULL.
> 
> This switches MemoryRegion to IOMMUMemoryRegion in most places except
> the ones where MemoryRegion may be an alias.
> 
> This defines memory_region_init_iommu_type() to allow creating
> IOMMUMemoryRegion subclasses. In order to support custom QOM type,
> this splits memory_region_init() to object_initialize() +
> memory_region_do_init.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

>  /**
> + * memory_region_init_iommu_type: Initialize a memory region of a custom type
> + * that translates addresses
> + *
> + * An IOMMU region translates addresses and forwards accesses to a target
> + * memory region.
> + *
> + * @typename: QOM class name
> + * @iommumr: the #IOMMUMemoryRegion to be initialized

<bikeshed>
I find "iommumr" terribly hard to read. Maybe iommu_mr is better? (Lots
of times in this patch.)
</bikeshed>

The s390 parts look fine.