Re: [Qemu-devel] [PATCH for-4.2 v10 08/15] virtio-iommu: Implement map/unmap

[Peter Xu <peterx@redhat.com>]

On Tue, Sep 03, 2019 at 01:37:11PM +0200, Auger Eric wrote:
> Hi Peter,
> 
> On 8/19/19 10:11 AM, Peter Xu wrote:
> > On Tue, Jul 30, 2019 at 07:21:30PM +0200, Eric Auger wrote:
> > 
> > [...]
> > 
> >> +    mapping = g_tree_lookup(domain->mappings, (gpointer)(&interval));
> >> +
> >> +    while (mapping) {
> >> +        viommu_interval current;
> >> +        uint64_t low  = mapping->virt_addr;
> >> +        uint64_t high = mapping->virt_addr + mapping->size - 1;
> >> +
> >> +        current.low = low;
> >> +        current.high = high;
> >> +
> >> +        if (low == interval.low && size >= mapping->size) {
> >> +            g_tree_remove(domain->mappings, (gpointer)(&current));
> >> +            interval.low = high + 1;
> >> +            trace_virtio_iommu_unmap_left_interval(current.low, current.high,
> >> +                interval.low, interval.high);
> >> +        } else if (high == interval.high && size >= mapping->size) {
> >> +            trace_virtio_iommu_unmap_right_interval(current.low, current.high,
> >> +                interval.low, interval.high);
> >> +            g_tree_remove(domain->mappings, (gpointer)(&current));
> >> +            interval.high = low - 1;
> >> +        } else if (low > interval.low && high < interval.high) {
> >> +            trace_virtio_iommu_unmap_inc_interval(current.low, current.high);
> >> +            g_tree_remove(domain->mappings, (gpointer)(&current));
> >> +        } else {
> >> +            break;
> >> +        }
> >> +        if (interval.low >= interval.high) {
> >> +            return VIRTIO_IOMMU_S_OK;
> >> +        } else {
> >> +            mapping = g_tree_lookup(domain->mappings, (gpointer)(&interval));
> >> +        }
> >> +    }
> >> +
> >> +    if (mapping) {
> >> +        qemu_log_mask(LOG_GUEST_ERROR,
> >> +                      "****** %s: Unmap 0x%"PRIx64" size=0x%"PRIx64
> >> +                     " from 0x%"PRIx64" size=0x%"PRIx64" is not supported\n",
> >> +                     __func__, interval.low, size,
> >> +                     mapping->virt_addr, mapping->size);
> >> +    } else {
> >> +        return VIRTIO_IOMMU_S_OK;
> >> +    }
> >> +
> >> +    return VIRTIO_IOMMU_S_INVAL;
> > 
> > Could the above chunk be simplified as something like below?
> > 
> >   while ((mapping = g_tree_lookup(domain->mappings, &interval))) {
> >     g_tree_remove(domain->mappings, mapping);
> >   }
> Indeed the code could be simplified. I only need to make sure I don't
> split an existing mapping.

Hmm... Do we need to still split an existing mapping if necessary?
For example when with this mapping:

  iova=0x1000, size=0x2000, phys=ADDR1, flags=FLAGS1

And if we want to unmap the range (iova=0, size=0x2000), then we
should split the existing mappping and leave this one:

  iova=0x2000, size=0x1000, phys=(ADDR1+0x1000), flags=FLAGS1

Right?

> 
> Also I needed to use g_tree_lookup_extended to retrieve the actual key
> to remove. The usage of g_tree_lookup_extended() allows me to remove the
> virt_addr and size fields from the mapping value value struct as those
> info can be retrieved from the key.

True.  Thanks,

-- 
Peter Xu