Re: [PATCH v3 3/3] tools: introduce parameter max_wp_ram_ranges.

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: George Dunlap [mailto:george.dunlap@citrix.com]
> Sent: 22 February 2016 17:23
> To: Paul Durrant
> Cc: Jan Beulich; Kevin Tian; Zhang Yu; Wei Liu; Ian Campbell; Andrew Cooper;
> xen-devel@lists.xen.org; Stefano Stabellini; Zhiyuan Lv; Ian Jackson; Keir
> (Xen.org)
> Subject: Re: [Xen-devel] [PATCH v3 3/3] tools: introduce parameter
> max_wp_ram_ranges.
> 
> On 22/02/16 17:01, Paul Durrant wrote:
> >> What you did in an earlier version of this series (correct me if I'm
> >> wrong) is to make a separate hypercall for memory, but still keep using
> >> the same internal implementation (i.e., still having a write_dm p2m type
> >> and using rangesets to determine which ioreq server to give the
> >> notification to).  But since the interface for memory looks exactly the
> >> same as the interface for MMIO, at some point this morphed back to "use
> >> xen_hvm_io_range but with a different range type (i.e., WP_MEM)".
> >>
> >
> > Yes, and that's now pointless since we're going to use purely p2m types for
> sending memory accesses to ioreq servers.
> >
> >> From an *interface* perspective that makes sense, because in both cases
> >> you want to be able to specify a domain, an ioreq server, and a range of
> >> physical addresses.  I don't have any objection to the change you made
> >> to hvm_op.h in this version of the series.
> >>
> >
> > No, if we are intercepting 'memory' purely by p2m type then there is no
> need for the additional range type.
> 
> So here seems to be the crux of our disagreement.
> 
> I don't understand why you think that the WP_MEM interface described in
> patch 2 of this series can't be implemented using p2m types rather than
> rangesets.
> 

Huh? I just said that's exactly how I intend to implement it:

"if we are intercepting 'memory' purely by p2m type then there is no need for the additional range type"

I.e. we will not intercept memory accesses by range, we will only intercept them by type.

  Paul

>  -George