Re: [RFC/PATCHSET 0/3] virtio: Implement virtio pstore device (v3)

From: Joel
Date: Wed Aug 24 2016 - 04:21:54 EST

Hi Namhyung,

> On Aug 23, 2016, at 8:20 AM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> Hi Joel,
> On Tue, Aug 23, 2016 at 7:25 PM, Joel Fernandes <agnel.joel@xxxxxxxxx> wrote:
>> From: Namhyung Kim <namhyung@xxxxxxxxxx>
>> 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 itâs

I believe the stock qemu wonât persist memory on its own without a reboot.
I found atleast one post where someone was trying to make mem-path
persist across a reboot and claimed to succeed:

> 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.

I agree, your approach is better for an emulated environment.


> Thanks,
> Namhyung