Re: [Xen-devel] [PATCH v5 8/9] libxc: rework of domain builder's page table handler

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 11/19/2015 01:09 AM, Juergen Gross wrote:
> On 18/11/15 17:21, Boris Ostrovsky wrote:
> > On 11/18/2015 11:16 AM, Wei Liu wrote:
> > > On Wed, Nov 18, 2015 at 11:11:16AM -0500, Boris Ostrovsky wrote:
> > > > On 11/12/2015 08:43 AM, Juergen Gross wrote:
> > > > > In order to prepare a p2m list outside of the initial kernel mapping
> > > > > do a rework of the domain builder's page table handler. The goal is
> > > > > to be able to use common helpers for page table allocation and setup
> > > > > for initial kernel page tables and page tables mapping the p2m list.
> > > > > This is achieved by supporting multiple mapping areas. The mapped
> > > > > virtual addresses of the single areas must not overlap, while the
> > > > > page tables of a new area added might already be partially present.
> > > > > Especially the top level page table is existing only once, of course.
> > > > >
> > > > > Currently restrict the number of mappings to 1 because the only mapping
> > > > > now is the initial mapping created by toolstack. There should not be
> > > > > behaviour change and guest visible change introduced.
> > > > >
> > > > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > > > Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx
> > > > > ---
> > > > >    tools/libxc/xc_dom_x86.c | 479
> > > > > ++++++++++++++++++++++++-----------------------
> > > > >    tools/libxc/xg_private.h |  39 +---
> > > > >    2 files changed, 252 insertions(+), 266 deletions(-)
> > > > This broke PVH. I get a triple fault (somewhere in clear_page(), so the
> > > > guest have run a little)
> > > Is there any output? We just noticed 32 bit pvgrub is broken. Not sure
> > > these two problems are related but the more information the better.
> > Not much:
> >
> > (d3) mapping kernel into physical memory
> > (XEN) d3v0 Triple fault - invoking HVM shutdown action 0
> >
> > I then looked at RIP and it was pointing to 'mov    %rax,(%rdi)' in
> > clear_page_orig(). I didn't check what %rdi was.
> I think I've found the bug. I dropped the special case for pvh to
> map page tables writable. Can you try the attached patch, please?

Yes, that fixes it. Thanks.

-boris

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