Re: [PATCH v2] tools/helpers: don't log errors when trying to load PVH xenstore-stubdom

[Andrew Cooper <amc96@xxxxxxxx>]

On 27/01/2023 10:55 am, Juergen Gross wrote:
>
> For xenstore-stubdom it is easier, as there is no reason to prefer
> the PV mode over PVH (in fact I'm still working on Xenstore LU for
> the PVH case, making the decision even easier).

I fully support having both PV and PVH options available.  It helps
maintain architecturally "clean" interfaces, and not decisions are about
performance.


But a PVH stub xenstored cannot outperform a equivalent PV stub
xenstored, for x86 architectural reasons.

PV stub xenstored doesn't do any of the usual things that causes PV
guests to be generally slow (different address spaces, user/kernel
context switching), and event/grants to PV guests is architecturally
more efficient than the HVM/PVH equivalents.

PV will never go away fully die, because we've got enough fastpaths
where this matters,  but I do expect that we'll eventually get to a
point where we don't have any general purpose OSes running as PV - only
single-task workloads such as stub xenstored.


The great thing about having both PV and PVH available is that people
will be able to see the concrete data confirming that PV is better,
without having to simply trust me on the matter.

~Andrew