On Fri, Jan 22, 2016 at 10:03:34AM +0000, David Vrabel wrote: > On 21/01/16 20:13, Daniel Kiper wrote: > > Linux kernel commit 054954eb051f35e74b75a566a96fe756015352c8 > > (xen: switch to linear virtual mapped sparse p2m list), which > > appeared in 3.19, introduced linear virtual mapped sparse p2m > > list. If readmem() reads p2m then it access this list using > > physical addresses. Sadly, VMA to physical address translation > > in crash requires access to p2m list. This means that we have > > a chicken and egg problem. In general this issue must be solved > > by introducing some changes in libxl, Linux kernel and crash > > (I have added this task to my long TODO list). However, in dom0 > > case we can use crash_xen_info_t.dom0_pfn_to_mfn_frame_list_list > > which is available out of the box. So, let's use it and make > > at least some users happy. > > I'm confused. How does a virtual address to (pseudo-)physical address > lookup require access to the p2m? Surely this is a walk of the page > tables followed by a M2P lookup on the MFN in the L1 PTE? Correct but crash does it a bit backward and scans p2m. I am not sure way, however, I am going to look at it during work on PV guests support. Daniel
