[PATCH v2 0/3] arm64: Drop support for VPIPT i-cache policy

[Anshuman Khandual]

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.