From: Jean-Philippe Brucker <redacted>
Sent: Thursday, September 30, 2021 6:33 PM

The PTE flags define whether the memory access is cache-coherent or not.
* WB is cacheable (short for write-back cacheable. Doesn't matter here
  what OI or RWA mean.)
* NC is non-cacheable.

         | Normal PCI access | No_snoop PCI access
  -------+-------------------+-------------------
  PTE WB | Cacheable         | Non-cacheable
  PTE NC | Non-cacheable     | Non-cacheable

This implies that PCI no-snoop supersedes PTE flags when it's supported
by the system?