Re: [PATCH 12/12] xen/x86: add hypercall performance counters for hvm, correct pv

[Juergen Gross <jgross@xxxxxxxx>]

On 21.10.21 17:19, Jan Beulich wrote:
> On 15.10.2021 14:51, Juergen Gross wrote:
> > The HVM hypercall handler is missing incrementing the per hypercall
> > counters. Add that.
> >
> > The counters for PV are handled wrong, as they are not using
> > perf_incra() with the number of the hypercall as index, but are
> > incrementing the total number of hypercalls only. Fix that.
> Why do you say "total number"? Isn't it that all accounting goes into
> set_trap_table's slot, effectively making that slot a "total number"
> despite not being labeled that way?
Oh, right. Will correct.

> Also this fix renders largely redundant the calls_to_multicall counter.
> Could I talk you into deleting that at the same time? (As to the "not
> fully redundant": I consider it suspicious that this counter gets
> incremented at the bottom of the function, not at the top.)
I think I'll just another patch doing that.

> Finally I take it that with the Kconfig setting being under DEBUG, we
> don't consider security supported builds with PERF_COUNTERS enabled.
> Otherwise as a prereq I would think perfc_incra() would need teaching
> of array_index_nospec().
I agree.

> In any event, preferably with at least the description slightly
> adjusted,
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks.


Juergen

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