Re: [PATCH] qemu/timer: Don't use RDTSC on i486

[Peter Maydell]

On Sat, 25 Nov 2023 at 12:24, Petr Cvek <petrcvekcz@gmail.com> wrote:
>
> GCC defines __i386__ for i386 and i486, which both lack RDTSC instruction.
> The i386 seems to be impossible to distinguish, but i486 can be identified
> by checking for undefined __i486__.
>
> Signed-off-by: Petr Cvek <petrcvekcz@gmail.com>

Last time this came up (over a decade ago!) we dropped the idea
because we couldn't find a consistent way of identifying
the no-RDTSC CPUs:
https://patchwork.ozlabs.org/project/qemu-devel/patch/1353683570-30525-1-git-send-email-peter.maydell@linaro.org/

We have already deprecated 32-bit x86 host support for
system emulation mode, incidentally.

thanks
-- PMM