Re: [PATCH v4 03/10] tools/libxl: add vmtrace_pt_size parameter

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

On Tue, Jun 30, 2020 at 02:33:46PM +0200, Michał Leszczyński wrote:
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 59bdc28c89..7b8289d436 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -92,6 +92,7 @@ struct xen_domctl_createdomain {
>      uint32_t max_evtchn_port;
>      int32_t max_grant_frames;
>      int32_t max_maptrack_frames;
> +    uint8_t vmtrace_pt_order;

I've been thinking about this, and even though this is a domctl (so
not a stable interface) we might want to consider using a size (or a
number of pages) here rather than an order. IPT also supports
TOPA mode (kind of a linked list of buffers) that would allow for
sizes not rounded to order boundaries to be used, since then only each
item in the linked list needs to be rounded to an order boundary, so
you could for example use three 4K pages in TOPA mode AFAICT.

Roger.