Re: [PATCH] virtio-iommu: Handle non power of 2 range invalidations

[Peter Xu <peterx@redhat.com>]

Eric,

On Thu, Feb 18, 2021 at 03:16:50PM +0100, Eric Auger wrote:
> @@ -164,12 +166,27 @@ static void virtio_iommu_notify_unmap(IOMMUMemoryRegion *mr, hwaddr virt_start,
>  
>      event.type = IOMMU_NOTIFIER_UNMAP;
>      event.entry.target_as = &address_space_memory;
> -    event.entry.addr_mask = virt_end - virt_start;
> -    event.entry.iova = virt_start;
>      event.entry.perm = IOMMU_NONE;
>      event.entry.translated_addr = 0;
> +    event.entry.addr_mask = mask;
> +    event.entry.iova = virt_start;
>  
> -    memory_region_notify_iommu(mr, 0, event);
> +    if (mask == UINT64_MAX) {
> +        memory_region_notify_iommu(mr, 0, event);
> +    }
> +
> +    size = mask + 1;
> +
> +    while (size) {
> +        uint8_t highest_bit = 64 - clz64(size) - 1;

I'm not sure fetching highest bit would work right. E.g., with start=0x11000
and size=0x11000 (then we need to unmap 0x11000-0x22000), current code will
first try to invalidate range (0x11000, 0x10000), that seems still invalid
since 0x11000 is not aligned to 0x10000 page mask.

I think the same trick in vtd_address_space_unmap() would work.  If you agree,
maybe we can generalize that get_naturally_aligned_size() out, but maybe with a
better name as a helper?

Thanks,

-- 
Peter Xu