aarch64: Enable use of FPMR
FEAT_FPMR adds the FPMR register. Acceses to FPMR (whether direct or
indirect) trap to EL3 unless SCR_EL3.EnFPM is set, and so boot-wrapper
support is necessary.
Support for FEAT_FPMR was added to Linux in v6.8 without any
boot-wrapper support. Consequently when FPMR is enabled in a model, the
kernel will hang when attempting to write to the FPMR (e.g. when
entering userspace for the first time).
Add boot-wrapper support for FEAT_FPMR, as described in the latest ARM
ARM (ARM DDI 0487 L.a), which can be found at:
https://developer.arm.com/documentation/ddi0487/la/?lang=en
The ID_AA64PFR2_EL1 ID register has existed as reserved RES0 space since
ARMv8.0 but only recently gained a name, and so older assemblers may not
be able to encode ID_AA64PFR2_EL1 directly. Thus we need an explicit
definition of the sysreg encoding to support these assemblers.
Cc: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250511095211.1638852-3-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
2 files changed
