Hello all,

We are sending this note to notify you of one of the breaking changes related to the enablement of FEAT_SVE in TF-A. This mainly impacts platforms which are configurable (FVP, QEMU, Total Compute).

FEAT_SVE has now been moved under the Feature detection mechanism wherein a CPU feature macro can have 3 possible states

* 0: FEAT_STATE_DISABLED * 1: FEAT_STATE_ALWAYS ( Always enabled, no runtime check) * 2: FEAT_STATE_CHECK (Dynamically check based on ID registers, done each time when feature registers are being accessed)

For platforms which have a single configuration, it's better to choose either disabled or enabled (as it is a bit faster as there is no dynamic check). For platforms which can have different HW configurations, it makes sense to put them under FEAT_STATE_CHECK(=2), so that they will boot with any configuration of HW.

Keeping this in mind, all configurable platforms (FVP, QEMU, TC) have been modified to adopt dynamic detection(FEAT_STATE_CHECK) for FEAT_SVE. [1]

SVE Patch Reference: [1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/20306

Best regards, Jayanth