On Thu, 13 Nov 2014 09:25:48 -0500 Vivek Goyal <vgoyal at redhat.com> wrote: > On Thu, Nov 13, 2014 at 05:30:21PM +0900, HATAYAMA, Daisuke wrote: > > > > (2014/11/13 17:06), Petr Tesarik wrote: > > >On Thu, 13 Nov 2014 09:17:09 +0900 (JST) > > >HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote: > > > > > >>From: Vivek Goyal <vgoyal at redhat.com> > > >>Subject: Re: [PATCH] kdump, x86: report actual value of phys_base in VMCOREINFO > > >>Date: Wed, 12 Nov 2014 17:12:05 -0500 > > >> > > >>>On Wed, Nov 12, 2014 at 03:40:42PM +0900, HATAYAMA Daisuke wrote: > > >>>>Currently, VMCOREINFO note information reports the virtual address of > > >>>>phys_base that is assigned to symbol phys_base. But this doesn't make > > >>>>sense because to refer to value of the phys_base, it's necessary to > > >>>>get the value of phys_base itself we are now about to refer to. > > >>>> > > >>> > > >>>Hi Hatayama, > > >>> > > >>>/proc/vmcore ELF headers have virtual address information and using > > >>>that you should be able to read actual value of phys_base. gdb deals > > >>>with virtual addresses all the time and can read value of any symbol > > >>>using those headers. > > >>> > > >>>So I am not sure what's the need for exporting actual value of > > >>>phys_base. > > >>> > > >> > > >>Sorry, my logic in the patch description was wrong. For /proc/vmcore, > > >>there's enough information for makedumpdile to get phys_base. It's > > >>correct. The problem here is that other crash dump mechanisms that run > > >>outside Linux kernel independently don't have information to get > > >>phys_base. > > > > > >Yes, but these mechanisms won't be able to read VMCOREINFO either, will > > >they? > > > > > > > I don't intend such sophisticated function only by VMCOREINFO. > > Search vmcore for VMCOREINFO using strings + grep before opening it by crash. > > I intend that only here. > > I think this is very crude and not proper way to get to vmcoreinfo. Same here. If VMCOREINFO must be locatable without communicating any information to the hypervisor, then I would rather go for something similar to what s390(x) folks do - a well-known location in physical memory that contains a pointer to a checksummed OS info structure, which in turn contains the VMCOREINFO pointers. I'm a bit surprised such mechanism is not needed by Fujitsu SADUMP. Or is that part of the current plan, Daisuke? Petr T
