Hi Joel, On Tue, Aug 23, 2016 at 7:25 PM, Joel Fernandes <agnel.j...@gmail.com> wrote: > From: Namhyung Kim <namhy...@kernel.org> > >> Hello, >> >> This is another iteration of the virtio-pstore work. In this patchset >> I addressed most of feedbacks from previous version and drooped the >> support for PSTORE_TYPE_CONSOLE for simplicity. It'll be added once the >> basic > > Hi Namhyung, > > This looks like a useful pstore backend. Great work.
Thanks! > > BTW, Have you considered using -mem-path in Qemu for this purpose? > I was thinking about using this, and then somehow have kernel reserve > a part of physical memory for the pstore. Then after the crash, or > whenever you want to read the contents of the pstore on the host, you > could just extract that part of the mem-path file. I wasn't aware of the -mem-path option and it seems that the existing ramoops pstore backend can take care of it. > > Any thoughts on what you think about it? In your approach though, you > wouldn't need a backing mem-path file which is the size of the guest > RAM (which could be as big as the mem-path file). I wonder if the > mem-path file can be created sparse, and/or Qemu has support to > configure a certain part of guest RAM as file-backed memory and the > rest of it from Anonymous memory (not backed by mem-path) so that > the size of the mem-path file can be kept at a minimum. The pstore (ramoops) requires the region of the memory is preserved across reboot. Is it possible when -mem-path is used? I think it's better to use a separate region/file for pstore rather than being a part of guest RAM or as you said, it'd be great if qemu supported such a hybrid mem-path. Also my approach can handle streams of data bigger than the pstore buffer size. Although we can extract the contents of mem-path file periodically, it might be hard for externel process to know the right time to extract and there's a possibility of information loss IMHO. Thanks, Namhyung
