> Am 28.02.2020 um 20:55 schrieb Peter Xu <pet...@redhat.com>:
>
> On Thu, Feb 27, 2020 at 11:12:02AM +0100, David Hildenbrand wrote:
>> +static void qemu_vfio_dma_map_resize(QEMUVFIOState *s, void *host,
>> + size_t old_size, size_t new_size)
>> +{
>> + IOVAMapping *m;
>> + int index = 0;
>> +
>> + qemu_mutex_lock(&s->lock);
>> + m = qemu_vfio_find_mapping(s, host, &index);
>> + if (!m) {
>> + return;
>> + }
>> + assert(m->size == old_size);
>> +
>> + /* Note: Not atomic - we need a new ioctl for that. */
>> + qemu_vfio_undo_mapping(s, m->iova, m->size);
>> + qemu_vfio_do_mapping(s, host, m->iova, new_size);
>
> Another way to ask my previous question 1 (in the other reply): Can we
> simply map/unmap the extra, while keep the shared untouched?
As far as I understand the kernel implementation, unfortunately no. You might
be able to grow (by mapping the delta), but shrinking is not possible AFAIR.
And I *think* with many resizes, there could be an issue if I remember
correctly.
Thanks!
>
> Thanks,
>
>> +
>> + m->size = new_size;
>> + assert(qemu_vfio_verify_mappings(s));
>> +
>> + qemu_mutex_unlock(&s->lock);
>> +}
>
> --
> Peter Xu
>
