RISCV Vector unit disabled by default for new task (was Re: [PATCH v12 17/17] riscv: prctl to enable vector commands)

[Darius Rad]

On Fri, Dec 09, 2022 at 11:02:57AM +0100, Florian Weimer wrote:
> * Andrew Waterman:
> 
> > This suggests that ld.so, early-stage libc, or possibly both will need
> > to make this prctl() call, perhaps by parsing the ELF headers of the
> > binary and each library to determine if the V extension is used.
> 
> If the string functions use the V extension, it will be enabled
> unconditionally.  So I don't see why it's okay for libc to trigger this
> alleged UAPI change, when the kernel can't do it by default.
> 

Because the call to enable can fail and userspace needs to deal with that.

// darius