diff options
| author | Mark Brown <broonie@kernel.org> | 2021-06-03 19:41:18 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-06-08 14:00:12 +0100 |
| commit | cfa7ff959a789a953eac40c8ac793e2cfc2db931 (patch) | |
| tree | 121241b7f3a9dfb8d374a06c9c4659f46d8f654f /drivers/firmware | |
| parent | 57ad4fe0859ec6dd15776cae6ee8a139492334fd (diff) | |
arm64: smccc: Support SMCCC v1.3 SVE register saving hint
SMCCC v1.2 requires that all SVE state be preserved over SMC calls which
introduces substantial overhead in the common case where there is no SVE
state in the registers. To avoid this SMCCC v1.3 introduces a flag which
allows the caller to say that there is no state that needs to be preserved
in the registers. Make use of this flag, setting it if the SMCCC version
indicates support for it and the TIF_ flags indicate that there is no live
SVE state in the registers, this avoids placing any constraints on when
SMCCC calls can be done or triggering extra saving and reloading of SVE
register state in the kernel.
This would be straightforward enough except for the rather entertaining
inline assembly we use to do SMCCC v1.1 calls to allow us to take advantage
of the limited number of registers it clobbers. Deal with this by having a
function which we call immediately before issuing the SMCCC call to make
our checks and set the flag. Using alternatives the overhead if SVE is
supported but not detected at runtime can be reduced to a single NOP.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210603184118.15090-1-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'drivers/firmware')
| -rw-r--r-- | drivers/firmware/smccc/smccc.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c index 028f81d702cc..9f937b125ab0 100644 --- a/drivers/firmware/smccc/smccc.c +++ b/drivers/firmware/smccc/smccc.c @@ -15,6 +15,7 @@ static u32 smccc_version = ARM_SMCCC_VERSION_1_0; static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE; bool __ro_after_init smccc_trng_available = false; +u64 __ro_after_init smccc_has_sve_hint = false; void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit) { @@ -22,6 +23,9 @@ void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit) smccc_conduit = conduit; smccc_trng_available = smccc_probe_trng(); + if (IS_ENABLED(CONFIG_ARM64_SVE) && + smccc_version >= ARM_SMCCC_VERSION_1_3) + smccc_has_sve_hint = true; } enum arm_smccc_conduit arm_smccc_1_1_get_conduit(void) |