Re: Fwd: [PATCH 0/18] Nested Virtualization: Overview

[Keir Fraser <keir.fraser@eu.citrix.com>]

On 15/04/2010 14:20, "Christoph Egger" <Christoph.Egger@amd.com> wrote:

> patch 03: change local_event_delivery_* to take vcpu argument.
>                   This prevents spurious xen crashes on guest shutdown/destroy
>                   with nestedhvm enabled.

Can you give an example of how this bug manifests? I don't really see how
nestedhvm would interact so unexpectedly with this rather pv-oriented
subsystem.

> patch 04: obsolete gfn_to_mfn_current and remove it.
>                   gfn_to_mfn_current is redundant to
> gfn_to_mfn(current->domain, ...)
>                   This patch reduces the size of patch 17.

This one (at least -- there may be others) needs an ack from Tim.

> patch 05: hvm_set_cr0: Allow guest to switch into paged real mode.
>                   This makes hvmloader boot when we use xen in xen.

What if we are not running a nestedhvm guest, or otherwise on a system not
supporting paged real mode? Is it wise to remove the check in that case?
Even where we *do* support nestedhvm, should all guest writes to CR0 be
allowed to bypass that check (Isn't paged real mode architecturally only
allowed to be entered via VMRUN)?

More generally, I will allow these patches to sit for a week or two to give
time for potential reviewers to digest them.

 Thanks,
 Keir