Michael Kelley <mikelley@xxxxxxxxxxxxx> writes: > From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Sent: Wednesday, September 23, 2020 8:48 AM >> >> On Wed, Sep 23, 2020 at 10:43:29AM +0800, Dave Young wrote: >> > + more people who may care about this param >> >> Paarty time!! >> >> (See below, didn't snip any comments) >> > On 09/21/20 at 08:45pm, Eric W. Biederman wrote: >> > > Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> writes: >> > > >> > > > On Fri, Sep 18, 2020 at 05:47:43PM -0700, Andrew Morton wrote: >> > > >> On Fri, 18 Sep 2020 11:25:46 +0800 Dave Young <dyoung@xxxxxxxxxx> wrote: >> > > >> >> > > >> > crash_kexec_post_notifiers enables running various panic notifier >> > > >> > before kdump kernel booting. This increases risks of kdump failure. >> > > >> > It is well documented in kernel-parameters.txt. We do not suggest >> > > >> > people to enable it together with kdump unless he/she is really sure. >> > > >> > This is also not suggested to be enabled by default when users are >> > > >> > not aware in distributions. >> > > >> > >> > > >> > But unfortunately it is enabled by default in systemd, see below >> > > >> > discussions in a systemd report, we can not convince systemd to change >> > > >> > it: >> > > >> > >> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fsyst >> emd%2Fsystemd%2Fissues%2F16661&data=02%7C01%7Cmikelley%40microsoft.com% >> 7C3631bae06f7147c0f92908d85fd7f2b2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0% >> 7C637364728378052956&sdata=9CUpPUxcKLLggbJ1bjubBjbFUAhPVeZhIc4yss8wAiU%3 >> D&reserved=0 >> > > >> > >> > > >> > Actually we have got reports about kdump kernel hangs in both s390x >> > > >> > and powerpcle cases caused by the systemd change, also some x86 cases >> > > >> > could also be caused by the same (although that is in Hyper-V code >> > > >> > instead of systemd, that need to be addressed separately). >> > > > >> > > > Perhaps it may be better to fix the issus on s390x and PowerPC as well? >> > > > >> > > >> > >> > > >> > Thus to avoid the auto enablement here just disable the param writable >> > > >> > permission in sysfs. >> > > >> > >> > > >> >> > > >> Well. I don't think this is at all a desirable way of resolving a >> > > >> disagreement with the systemd developers >> > > >> >> > > >> At the above github address I'm seeing "ryncsn added a commit to >> > > >> ryncsn/systemd that referenced this issue 9 days ago", "pstore: don't >> > > >> enable crash_kexec_post_notifiers by default". So didn't that address >> > > >> the issue? >> > > > >> > > > It does in systemd, but there is a strong interest in making this on >> > > > by default. >> > > >> > > There is also a strong interest in removing this code entirely from the >> > > kernel. >> > >> > Added Hyper-V people and people who created the param, it is below >> > commit, I also want to remove it if possible, let's see how people >> > think, but the least way should be to disable the auto setting in both systemd >> > and kernel: > > Hyper-V uses a notifier to inform the host system that a Linux VM has > panic'ed. Informing the host is particularly important in a public cloud > such as Azure so that the cloud software can alert the customer, and can > track cloud-wide reliability statistics. Whether a kdump is taken is controlled > entirely by the customer and how he configures the VM, and we want > the host to be informed either way. Why? Why does the host care? Especially if the VM continues executing into a kdump kernel? Further like I have mentioned everytime something like this has come up a call on the kexec on panic code path should be a direct call (That can be audited) not something hidden in a notifier call chain (which can not). Eric _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
