Messages in this thread |  | | Date | Sun, 20 Dec 2015 20:59:44 +0100 | From | Peter Zijlstra <> | Subject | Re: [Xen-devel] new barrier type for paravirt (was Re: [PATCH] virtio_ring: use smp_store_mb) |
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On Sun, Dec 20, 2015 at 05:07:19PM +0000, Andrew Cooper wrote: > > Very much +1 for fixing this. > > Those names would be fine, but they do add yet another set of options in > an already-complicated area. > > An alternative might be to have the regular smp_{w,r,}mb() not revert > back to nops if CONFIG_PARAVIRT, or perhaps if pvops have detected a > non-native environment. (I don't know how feasible this suggestion is, > however.)
So a regular SMP kernel emits the LOCK prefix and will patch it out with a DS prefix (iirc) when it finds but a single CPU. So for those you could easily do this.
However an UP kernel will not emit the LOCK and do no patching.
So if you're willing to make CONFIG_PARAVIRT depend on CONFIG_SMP or similar, this is doable.
I don't see people going to allow emitting the LOCK prefix (and growing the kernel text size) for UP kernels.
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