Re: [PATCH v2 1/2] s390x/pci: add support for guests that request direct mapping

[Matthew Rosato]

>>> +{
>>> +    MachineState *ms = MACHINE(qdev_get_machine());
>>> +
>>> +    /*
>>> +     * For direct-mapping we must map the entire guest address space.  
>>> Rather
>>> +     * than using an iommu, create a memory region alias that maps GPA X to
>>> +     * iova X + SDMA.  VFIO will handle pinning via its memory listener.
>>> +     */
>>> +    g_autofree char *name = g_strdup_printf("iommu-dm-s390-%04x",
>>> +                                            iommu->pbdev->uid);
>>> +    memory_region_init_alias(&iommu->dm_mr, OBJECT(&iommu->mr), name, 
>>> ms->ram,
>>> +                             0, ms->ram_size);
>>
>> Is it a good idea to take the whole machine ram-size here?
>> Could it be better to pass it as qdev property?
> 
> I think we want all guest RAM, just like ordinary vfio on !s390x without a 
> viommu would do.
> 
> Matthew, I assume to handle virtio-mem, we would actually pass in here the 
> result from s390_get_memory_limit(), which will cover initial+device RAM, 
> correct? Until then, this would map initial RAM only.
> 

Good point.  Using s390_get_memory_limit() sounds good to me; That will make v3 
of this series dependent on the s390x virtio-mem series but sounds like you're 
sending that sometime this week anyway.

I'll start testing on top of that with something like..

memory_region_init_alias(&iommu->dm_mr, OBJECT(&iommu->mr), name, ms->ram,
                         0, s390_get_memory_limit(s390ms));