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

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

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@suse.com>
>>>>> Reviewed-by: Wei Liu <wei.liu2@citrix.com
>>>>> ---
>>>>>    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