----- Original Message ----- > On 04/26, Dave Anderson wrote: > > > > > > ----- Original Message ----- > > > On 04/26, Dave Anderson wrote: > > > > > > > > > No, just a regular file, qemu creates it and does mmap(MAP_SHARED) on > > > > > it. > > > > > > > > > > > that constantly contains the > > > > > > current contents of the guest's physical memory? > > > > > > > > > > Yes, > > > > > > > > > > > Is it like /dev/mem? > > > > > > > > > > yes, but more like /dev/crash. > > > > > > > > > > Oleg. > > > > > > > > Unfortunately I am completely unfamiliar with qemu option > > > > specifications. > > > > > > I too do not know much about qemu options, > > > > > > > So if I were to log into the guest machine, does a /tmp/MEM file exist? > > > > > > No, > > > > > > > Or does it exist on the host machine? > > > > > > Yes, it is just the normal file on the host which runs qemu. > > > > > > Well, "normal" is not neccessarily true in that you can use, for example, > > > > > > mem-path=/path/to/hugetlb-mount/... > > > > > > but this doesn't matter. It is still the "regular" file mmaped by qemu, > > > the > > > host can read it to acess the guest's physical memory. > > > > > > Oleg. > > > > OK, so we're running on a host machine that has one of these memory files > > that is accessible as a regular file. > > Yes, and this file is the physical memory of the guest. So it is essentially > the RAM dump which can be used by "crash PATH-TO-THIS-FILE@0" right now without > any patches. And in this particular case the offset is always zero. > > But not on x86-64, is_ramdump() insists on ramdump_to_elf() even if we could > use read_ramdump(), and ramdump_to_elf() doesn't support x86-64. Right, but that's a trivial fix, right? As I mentiond before, the only reason it doesn't support is because nobody's tried/asked/needed-to. And with x86_64 support put into place, at least the "non-live" file should be a considered a ramdump, right? > And of course, you can't use this RAM dump in "live" mode (without these > changes). Right -- that's the rub here. The "live version of a dumpfile" is a hybrid that's never been considered before. > > So what's the remote access needed > > for -- just to query for the particulars of the layout of the memory file? > > Sorry, I don't understand... > > Do you ask me what qemu does with this file or what? This is where I totally got off on the wrong foot. I thought you had mentioned something about remote gdb protocol, or something along those lines where there was some remote communication protocal? I'm sorry about that, I really went off into the weeds... Dave -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
