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&gt; 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&gt; 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.