Re: Why does glibc use AVX-512?

[H.J. Lu]

On Fri, Mar 26, 2021 at 1:35 PM Florian Weimer <fw@xxxxxxxxxxxxx> wrote:

>
> All this needs to work transparently without user intervention.  We
> cannot require firmware upgrades to fix the incorrect RTM reporting
> issue (the bug I referenced).  I think we can require software updates
> which tell glibc when to use RTM-enabled string functions if the
> dynamic selection does not work (either for performance reasons, or
> because of the RTM reporting bug).
>
> I want to avoid a situation where one in eight processes fail to work
> correctly because the CPUID checks ran on CPU 0, where RTM is reported
> as available, and then we trap when executing XTEST on other CPUs.

glibc can disable RTM based on CPU model and stepping.

-- 
H.J.