Re: [Crash-utility] [Xen-devel] crash tool - problem with new Xen linear virtual mapped sparse p2m list
On 24/11/15 10:17, Petr Tesarik wrote:
On Tue, 24 Nov 2015 10:09:01 +0000
David Vrabel <david.vrabel(a)citrix.com> wrote:
> On 24/11/15 09:55, Malcolm Crossley wrote:
>> On 24/11/15 08:59, Jan Beulich wrote:
>>>>>> On 24.11.15 at 07:55, <JGross(a)suse.com> wrote:
>>>> What about:
>>>>
>>>> 4) Instead of relying on the kernel maintained p2m list for m2p
>>>> conversion use the hypervisor maintained m2p list which should be
>>>> available in the dump as well. This is the way the alive kernel is
>>>> working, so mimic it during crash dump analysis.
>>> I fully agree; I have to admit that looking at the p2m when doing page
>>> table walks for a PV Dom0 (having all machine addresses in page table
>>> entries) seems kind of backwards. (But I say this knowing nothing
>>> about the tool.)
>>>
>> I don't think we can reliably use the m2p for PV domains because
>> PV domains don't always issue a m2p update hypercall when they change
>> their p2m mapping.
> This only applies to foreign pages which won't be very interesting to a
> crash tool.
True. I think the main reason crash hasn't done this is that it cannot
find the hypervisor maintained m2p list. It should be sufficient to add
some more fields to XEN_VMCOREINFO, so that crash can locate the
mapping in the dump.
The M2P lives at an ABI-specified location in all virtual address spaces
for PV guests.
Either 0xF5800000 or 0xFFFF800000000000 depending on bitness.
This will be more compatible to use, as it won't depend on a newer
hypervisor with modified notes.
~Andrew