Re: [Xen-devel] [PATCH RFC v1 00/13] Introduce HMV without dm and new boot ABI

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

Hello,

El 22/06/15 a les 19.55, Stefano Stabellini ha escrit:
> Hi Roger,
> 
> given that this patch series is actually using the Xen "hvm" builder, I
> take that all the PVH code paths in Xen or the guest kernel are not
> actually used, correct? This is more like PV on HVM without QEMU, right?

From a Xen POV this is not a PVH guest (it's an HVM guest), although I'm
using some code paths which are shared with PVH. In the guest (in this
case FreeBSD) I'm using the same paths as PVH, since the exposed
interface is very similar. We probably aim at enabling the same set of
hypercalls that are enabled on PVH.

> Do you think think this can work for Dom0 too?

I don't see why it couldn't be made to work.

> Would that make all the PVH stuff in Xen and Linux effectively useless?

No, I expect that some code paths inside of Xen will be shared between
PVH and this HVM-without-dm guest type.

Then from a guest POV the interface is quite similar, so most of the
code present in Linux and FreeBSD in order to run as a PVH guest can be
reused for this new guest mode. If you take a look at the FreeBSD patch
the change is just mostly during early boot in order to set the page
tables and jump into long mode, then the rest is quite similar to PVH.

Forgot to mention, I've also tested it with hap=0 (so using shadow) and
it seems to work fine.

Roger.

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