On Thu, May 16, 2024 at 02:31:59PM -0600, Alex Williamson wrote: > Yes, exactly. Zero'ing the page would obviously reestablish the > coherency, but the page could be reallocated without being zero'd and as > you describe the owner of that page could then get inconsistent > results. I think if we care about the performance of this stuff enough to try and remove flushes we'd be better off figuring out how to disable no snoop in PCI config space and trust the device not to use it and avoid these flushes. iommu enforcement is nice, but at least ARM has been assuming that the PCI config space bit is sufficient. Intel/AMD are probably fine here as they will only flush for weird GPU cases, but I expect ARM is going to be unhappy. Jason
