Re: [PATCH 00/34] arch: barrier cleanup + __smp_xxx barriers for virt

[Michael S. Tsirkin]

On Wed, Dec 30, 2015 at 03:46:46PM -0500, David Miller wrote:
> From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> Date: Wed, 30 Dec 2015 14:58:19 +0200
> 
> > -. Patch 1 documents the __smp APIs, and explains why they are
> >    useful for virt
> 
> If virt is doing things like interacting with descriptors that are
> shared with a (potentially SMP) host, why don't we just annotate those
> specific cases?

Using a bunch of per-arch ifdefs in virtio?
That's fundamentally what we have now.

But basically the rework reduces the LOC count in kernel anyway
by moving all ifdef CONFIG_SMP hacks into asm-generic.
So why not let virt benefit?

Or do you mean wrappers for __smp_XXX that explicitly
say they are for talking to host?
E.g. pv_mb() pv_rmb() etc.
That sounds very reasonable to me.

__smp_XXX things then become an implementation detail.

> The other memory barriers in the kernel do not matter for SMP'ness
> when build UP.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/