> From: Wathsala Wathawana Vithanage <wathsala.vithanage@xxxxxxx> > Sent: Friday, March 14, 2025 9:49 AM > > > > > > Having said that, regardless of this proposal or the availability of kernel > > > TPH support, a VFIO driver could enable TPH and set an arbitrary ST on > the > > > MSI-X/ST table or a device-specific location on supported platforms. If the > > > driver doesn't have a list of valid STs, it can enumerate 8- or 16-bit STs > and > > > measure access latencies to determine valid ones. > > > > > > > PCI capabilities are managed by the kernel VFIO driver. So w/o this > > patch no userspace driver can enable TPH to try that trick? > > Yes, it's possible. It's just a matter of setting the right bits in the PCI config > space to enable TPH on the device. > No. Before this patch the TPH capability is read-only to userspace, enforced by vfio-pci. So there is no way that an user can toggle the TPH cap by itself!
