On 07/28/17 16:52, Marc-André Lureau wrote: > Hi Dave > > On Wed, Jul 26, 2017 at 10:21 AM, Michael S. Tsirkin <m...@redhat.com> wrote: >> On Sat, Jul 15, 2017 at 01:47:50AM +0200, Marc-André Lureau wrote: >>>> >>>> There's more info scattered in other places. >>>> >>>> Why do you get to document it? Because you are the one exposing it >>>> across the hypervisor/vm boundary where it will need to be >>>> understood by people/tools not running within guest. >>>> >>>> So "just read the script in qemu source" is not how an interface >>>> should be documented. >>> >>> I don't understand the issue, it's a kernel ELF note that qemu passes >>> for dump/crash tools in the dump headers/sections. >> >> The way it looks to me, this patchset is exposing an internal kernel >> detail and making it part of ABI maybe it already is, my point was 1. >> should we get a confirmation from upstream it's not going to change? 2. >> if it's ABI let's document what do we expect to be there. > > > Could you help explain the expectations and stability guarantees of > vmcoreinfo ELF note ? > > I am a bit stuck here, after all, vmcoreinfo is mostly used by crash > so I thought you could help. > > The only thing qemu does with it is try to get NUMBER(phys_base)= > field to update the phys_base used in the various dump headers. (this > could be dropped, and qemu ignoring the note content, if the debug > tools take vmcoreinfo values with higher priority than other header > fields)
I agree; if "crash" guarantees that the vmcoreinfo note will override whatever phys_base value QEMU may have guessed otherwise (from other places) and written to some dedicated phys_base header fields, then in QEMU we don't have to propagate phys_base from the vmcoreinfo note to said other fields -- we can treat the vmcoreinfo note entirely opaquely. Thanks Laszlo > >> But again since there's not a whole lot of documentation here >> that you provided, I might be misunderstanding completely. > > Because there isn't much available in the kernel either, except > Documentation/ABI/testing/sysfs-kernel-vmcoreinfo. > >