feat(smccc): implement SMCCC_ARCH_FEATURE_AVAILABILITY
SMCCC_ARCH_FEATURE_AVAILABILITY [1] is a call to query firmware about
the features it is aware of and enables. This is useful when a feature
is not enabled at EL3, eg due to an older FW image, but it is present in
hardware. In those cases, the EL1 ID registers do not reflect the usable
feature set and this call should provide the necessary information to
remedy that.
The call itself is very lightweight - effectively a sanitised read of
the relevant system register. Bits that are not relevant to feature
enablement are masked out and active low bits are converted to active
high.
The implementation is also very simple. All relevant, irrelevant, and
inverted bits combined into bitmasks at build time. Then at runtime the
masks are unconditionally applied to produce the right result. This
assumes that context managers will make sure that disabled features
do not have their bits set and the registers are context switched if
any fields in them make enablement ambiguous.
Features that are not yet supported in TF-A have not been added. On
debug builds, calling this function will fail an assert if any bits that
are not expected are set. In combination with CI this should allow for
this feature to to stay up to date as new architectural features are
added.
If a call for MPAM3_EL3 is made when MPAM is not enabled, the call
will return INVALID_PARAM, while if it is FEAT_STATE_CHECK, it will
return zero. This should be fairly consistent with feature detection.
The bitmask is meant to be interpreted as the logical AND of the
relevant ID registers. It would be permissible for this to return 1
while the ID returns 0. Despite this, this implementation takes steps
not to. In the general case, the two should match exactly.
Finally, it is not entirely clear whether this call replies to SMC32
requests. However, it will not, as the return values are all 64 bits.
[1]: https://developer.arm.com/documentation/den0028/galp1/?lang=en
Co-developed-by: Charlie Bareham <charlie.bareham@arm.com>
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I1a74e7d0b3459b1396961b8fa27f84e3f0ad6a6f
diff --git a/Makefile b/Makefile
index 6f080b4..45b0b21 100644
--- a/Makefile
+++ b/Makefile
@@ -959,6 +959,10 @@
ifneq (${ENABLE_FEAT_FPMR},0)
$(error "ENABLE_FEAT_FPMR cannot be used with ARCH=aarch32")
endif
+
+ ifeq (${ARCH_FEATURE_AVAILABILITY},1)
+ $(error "ARCH_FEATURE_AVAILABILITY cannot be used with ARCH=aarch32")
+ endif
endif #(ARCH=aarch32)
ifneq (${ENABLE_FEAT_FPMR},0)
@@ -1207,6 +1211,7 @@
PROGRAMMABLE_RESET_ADDRESS \
PSCI_EXTENDED_STATE_ID \
PSCI_OS_INIT_MODE \
+ ARCH_FEATURE_AVAILABILITY \
RESET_TO_BL31 \
SAVE_KEYS \
SEPARATE_CODE_AND_RODATA \
@@ -1388,6 +1393,7 @@
PROGRAMMABLE_RESET_ADDRESS \
PSCI_EXTENDED_STATE_ID \
PSCI_OS_INIT_MODE \
+ ARCH_FEATURE_AVAILABILITY \
RESET_TO_BL31 \
RME_GPT_BITLOCK_BLOCK \
RME_GPT_MAX_BLOCK \