Re: [PATCH v3 5/5] intel_iommu: Optimize out some unnecessary UNMAP calls

[Peter Xu <peterx@redhat.com>]

On Thu, Jun 08, 2023 at 05:52:31PM +0800, Zhenzhong Duan wrote:
>      while (remain >= VTD_PAGE_SIZE) {
> -        IOMMUTLBEvent event;
>          uint64_t mask = dma_aligned_pow2_mask(start, end, s->aw_bits);
>          uint64_t size = mask + 1;
>  
>          assert(size);
>  
> -        event.type = IOMMU_NOTIFIER_UNMAP;
> -        event.entry.iova = start;
> -        event.entry.addr_mask = mask;
> -        event.entry.target_as = &address_space_memory;
> -        event.entry.perm = IOMMU_NONE;
> -        /* This field is meaningless for unmap */
> -        event.entry.translated_addr = 0;
> -
> -        memory_region_notify_iommu_one(n, &event);
> +        map.iova = start;
> +        map.size = mask;
> +        if (iova_tree_find(as->iova_tree, &map)) {
> +            event.entry.iova = start;
> +            event.entry.addr_mask = mask;
> +            memory_region_notify_iommu_one(n, &event);
> +        }

Ah one more thing: I think this path can also be triggered by notifiers
without MAP event registered, whose iova tree will always be empty.  So we
may only do this for MAP, then I'm not sure whether it'll be worthwhile..

-- 
Peter Xu