[PATCH v2 0/4] arm64: Add AT_HWCAP3

[Szabolcs Nagy]

The 07/05/2022 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?

AT_HWCAP2 top bits works for me too.

then i'd do AT_HWCAP3 when we run out of hwcap2 bits.
i don't think defining AT_HWCAP3 without having any
hwcap3 bit is very useful.

this way we can postpone AT_HWCAP3 a bit and avoid
issues with top bits of plain AT_HWCAP in glibc.