Re: [PATCH v4 10/10] tools/proctrace: add proctrace tool

[Wei Liu <wl@xxxxxxx>]

On Thu, Jul 02, 2020 at 04:10:57PM +0100, Andrew Cooper wrote:
[...]
> 
> > +#include <stdlib.h>
> > +#include <stdio.h>
> > +#include <sys/mman.h>
> > +#include <signal.h>
> > +
> > +#include <xenctrl.h>
> > +#include <xen/xen.h>
> > +#include <xenforeignmemory.h>
> > +
> > +#define BUF_SIZE (16384 * XC_PAGE_SIZE)
> 
> This hardcodes the size of the buffer which is configurable per VM. 
> Mapping the buffer fails when it is smaller than this.
> 
> It appears there is still outstanding bug from the acquire_resource work
> which never got fixed.  The guest_handle_is_null(xmar.frame_list) path
> in Xen is supposed to report the size of the resource, not the size of
> Xen's local buffer, so userspace can ask "how large is this resource".
> 
> I'll try and find some time to fix this and arrange for backports, but
> the current behaviour is nonsense, and problematic for new users.

I can't quite figure out if this is a blocking comment of this tool to
be accepted. Can you clarify?

Wei.

> 
> ~Andrew