Re: [Xen-devel] [for-4.10] Re: [PATCH v2] tools/libxl: mark special pages as reserved in e820 map for PVH

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

On Wed, Dec 06, 2017 at 12:22:00PM +0100, Juergen Gross wrote:
> On 06/12/17 10:53, Julien Grall wrote:
> > Hi Juergen,
> > 
> > On 12/05/2017 04:19 PM, Juergen Gross wrote:
> >> On 05/12/17 16:23, Julien Grall wrote:
> >>> Hi Juergen,
> >>>
> >>> On 04/12/17 15:49, Juergen Gross wrote:
> >>>> On 21/11/17 12:06, Juergen Gross wrote:
> >>>>> The "special pages" for PVH guests include the frames for console and
> >>>>> Xenstore ring buffers. Those have to be marked as "Reserved" in the
> >>>>> guest's E820 map, as otherwise conflicts might arise later e.g. when
> >>>>> hotplugging memory into the guest.
> >>>>>
> >>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >>>>> ---
> >>>>> This is a bugfix for PVH guests. Please consider for 4.10.
> >>>>
> >>>> Ping?
> >>>
> >>> I was waiting an ack from tools maintainers before looking for a release
> >>> perspective.
> >>>
> >>> I would recommend to tag your patch is 4.10 to help reviewers prioritize
> >>> review on your patch. I have done it now.
> >>>
> >>> I am looking at releasing Xen 4.10 in the next few days. Can you explain
> >>> the pros/cons of this patch?
> >>
> >> Pros: PVH guests with 4GB of memory or more will work. :-)
> > 
> > They never worked before? Or is it a regression? If it is a regression
> > when did it appear?
> 
> Hmm, seems we are lucky: Linux kernel will not try to map any memory
> there (I just tested it). So we don't need that patch in 4.10 for Linux
> running as PVH guest. Not sure about BSD, though.

I haven't yet committed any PVHv2 support to FreeBSD, but in any case
I always avoid using memory below 4GB just in case...

Roger.

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