Arm provides multiple helpers to clean & invalidate the cache
for a given region. This is, for instance, used when allocating
guest memory to ensure any writes (such as the ones during scrubbing)
have reached memory before handing over the page to a guest.

Unfortunately, the arithmetics in the helpers can overflow and would
then result to skip the cache cleaning/invalidation. Therefore there
is no guarantee when all the writes will reach the memory.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-34321
• https://xenbits.xenproject.org/xsa/advisory-437.html