On 11/27/23 22:56, Marc Zyngier wrote: > ARMv8.2 introduced support for VPIPT i-caches, the V standing for > VMID-tagged. Although this looks like a reasonable idea, no > implementation has ever made it into the wild. > > Linux has supported this for over 6 years (amusingly, just as the > architecture was dropping support for AVIVT i-caches), but we had no > way to even test it, and it is likely that this code was just > bit-rotting. > > However, in a recent breakthrough (XML drop 2023-09, tagged as > d55f5af8e09052abe92a02adf820deea2eaed717), the architecture has > finally been purged of this option, making VIPT and PIPT the only two > valid options. Indeed, FEAT_VPIPT has been dropped from the 2023-09 document release. https://developer.arm.com/documentation/ddi0601/2023-06/AArch64-Registers/CTR-EL0--Cache-Type-Register CTR_EL0.L1Ip[15:14] = 00 - VMID aware Physical Index, Physical tag (VPIPT) with FEAT_VPIPT https://developer.arm.com/documentation/ddi0601/2023-09/AArch64-Registers/CTR-EL0--Cache-Type-Register CTR_EL0.L1Ip[15:14] = 00 - Reserved.
