[PATCH v2 0/4] arm64: Add AT_HWCAP3

[Marc Zyngier]

On 2022-07-05 18:53, Mark Brown wrote:
> On Mon, Jun 20, 2022 at 01:54:47PM +0100, Mark Brown wrote:
>> Currently for arm64 we expose hwcaps to userspace using the low 32 
>> bits
>> of AT_HWCAP and AT_HWCAP2. Due to the ever expanding capabilties of 
>> the
>> architecture we have now allocated all the available bits in this 
>> scheme
>> so we need to expand, either using the higher bits or adding a new
>> AT_HWCAP3. Discussions with glibc developers suggested that AT_HWCAP3
>> would be cleaner for them so the series adopts that approach.
> 
> This discussion appears to have ground to a halt.  Szabolcs prefers
> AT_HWCAP3, Catalin using the high bits of AT_HWCAP2 for now and nobody
> else said anything.  I don't have strong preferences either way but
> wonder if it's worth defining AT_HWCAP3 even if we start allocating 
> more
> bits from AT_HWCAP2 so that it's got more time to percolate through
> libcs and so on before it's actually needed.
> 
> What should we do here?

I really don't like the idea of adding a new HWCAP when we still
have free bits lying around. We should use that first, and only
add HWCAP3 once we are at (or close enough to) the limit.

That's assuming that there is no breakage with using these spare
bits. If something is at risk, I'd be good to spell it out.

         M.
-- 
Jazz is not dead. It just smells funny...