Re: [PATCH v4 2/4] x86/spec-ctrl: defer context-switch IBPB until guest entry

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Feb 14, 2023 at 05:11:05PM +0100, Jan Beulich wrote:
> In order to avoid clobbering Xen's own predictions, defer the barrier as
> much as possible. Merely mark the CPU as needing a barrier issued the
> next time we're exiting to guest context.

While I understand that doing the flush in the middle of the guest
context might not be ideal, as it's my understanding we also
needlessly flush Xen predictions, I'm unsure whether this makes any
difference in practice, and IMO just makes the exit to guest paths
more complex.

Thanks, Roger.