[PATCH v6] arm64: smccc: Support SMCCC v1.3 SVE register saving hint

[Mark Brown]

On Tue, Jun 08, 2021 at 01:15:33PM +0100, Will Deacon wrote:
> On Thu, Jun 03, 2021 at 07:41:18PM +0100, Mark Brown wrote:
> > 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

> > v6:
> >  - Prototype __arm_smccc_sve_check add add the _arm to the name to fix
> >    issues with symbol versioning.

> Can you elaborate on what was going wrong with symbol versioning, please?
> Are we papering over another genksyms bug here?

There's a requirement for a prototype to appear in asm-prototypes.h for
any symbol that's exported, even if it is never and should never be
referenced from C code.  I don't know if it's papering over a bug, looks
more like it's how things are supposed to work but just not documented
well (and symbol versions aren't turned on in defconfig).
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