Re: [Qemu-devel] [PATCH v7 05/27] tcg: add options for enabling MTTCG

[Richard Henderson]

On 01/19/2017 09:04 AM, Alex Bennée wrote:
> +void qemu_tcg_configure(QemuOpts *opts, Error **errp)
> +{
> +    const char *t = qemu_opt_get(opts, "thread");
> +    if (t) {
> +        if (strcmp(t, "multi") == 0) {
> +            if (TCG_OVERSIZED_GUEST) {
> +                error_setg(errp, "No MTTCG when guest word size > hosts");

I agree with this, since I don't ever imagine it'll be fixed.  It's a silly use
case in the first place considering the ubiquity of 64-bit hosts.

> +            } else if (!check_tcg_memory_orders_compatible()) {
> +                error_setg(errp,
> +                           "No MTTCG when guest MO is stronger than host 
> MO");

This, on the other hand, means that one cannot even force multi for testing.  A
warning perhaps?  And how shall we handle a guest translate adding barriers as
necessary to satisfy host memory ordering?


r~