On Thu, Sep 12, 2024 at 05:45:45PM +0100, Catalin Marinas wrote: > On Fri, Sep 06, 2024 at 12:05:23AM +0100, Mark Brown wrote: > > We will at some point need to bite this bullet but we need to decide if > > it's now or later. Given that we used the high bits of AT_HWCAP2 first > > and AT_HWCAP3 is already defined it feels like that might be people's > > preference, in order to minimise churn in serieses adding new HWCAPs > > it'd be good to get consensus if that's the case or not. > Since the arm64 ABI documents that only bits 62 and 63 from AT_HWCAP are > reserved for glibc, I think we should start using the remaining 30 bits > of AT_HWCAP first before going for AT_HWCAP3. I'm sure we'll go through > them quickly enough, so these two patches will have to be merged at some > point. That does seem like the easiest path for everyone, assuming that there hasn't been any usage of the remaining spare bits we weren't aware of. > We'll need an Ack from the (arm64) glibc people on the GCS patch series > if we are going for bits 32+ in AT_HWCAP. Yup, hopefully Yuri or Wilco can confirm prior to reposting. It does seem like it'd be good for glibc to add whatever support is needed for HWCAP3/4 now anyway so that whenever we do burn through the remaining bits on AT_HWCAP there's less friction as we start using them.
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