Re: [Qemu-devel] [PATCH 01/13] target/arm: Add ARM_FEATURE_SWP

[Richard Henderson]

On 9/15/18 6:32 PM, Peter Maydell wrote:
> In the current scheme of doing things I'd look for whether
> we could say that some more generic thing implied SWP
> rather than setting it in a lot of initfns (eg v5-but-not-v7VE?),
> but maybe the later patches make that a bad approach
> (haven't looked at the meat of this series).

Perhaps.  But indeed this goes back to the main question
posed in the cover letter.

> We want to arrange to have SWP work anyway on linux-user,
> I think, since the kernel will typically trap-and-emulate
> it assuming it was built with CONFIG_SWP_EMULATE. (I don't
> know if those kernels will advertise swp in the hwcaps,
> but I guess not.)

Ah, I did not know about SWP_EMULATE.  It appears to be
specific to armv7+ (though we don't support the pre-v4
cpus for which it might otherwise be relevant).

It does appear that HWCAP_SWP is advertised anyway:

mm/proc-v7.S:   .long   HWCAP_SWP | HWCAP_HALF | HWCAP_THUMB | HWCAP_FAST_MULT


r~