On Tue, Aug 06, 2024 at 03:50:45PM -0500, Michael Galaxy wrote:
Hi, On 8/6/24 07:38, Martin Kletzander wrote:On Wed, Jun 05, 2024 at 04:37:36PM -0400, mgalaxy@xxxxxxxxxx wrote:From: Michael Galaxy <mgalaxy@xxxxxxxxxx> if (src->mem.source != dst->mem.source) { - virReportError(VIR_ERR_CONFIG_UNSUPPORTED, - _("Target memoryBacking source '%1$s' doesn't match source memoryBacking source'%2$s'"), - virDomainMemorySourceTypeToString(dst->mem.source), - virDomainMemorySourceTypeToString(src->mem.source)); - return false; + /* + * The current use case for this is the live migration of live-update + * capable CPR guests mounted on PMEM devices at the hostDoes libvirt need more adjustments to support cpr-reboots? I don't think we have any support for them yet.Ummmm, no, not really, no. Which is a good question. CPR has two different modes. "reboots" and "execs". The former is when you want to do a full kexec (which blows away libvirt because you're rebooting), and the latter does not do a kexec at all. We are only currently using the reboot mode. And it works just fine. There are a number of QMP commands that CPR uses, but we are feeding those commands through libvirt with just the normal qmp command support that it already provides rather than doing any "built-in" changes to libvirt to support those features, currently. So, no, we don't have a need (currently) to further modify libvirt to support CPR.
The QMP command is fine, but since it messes with the VM behind libvirt's back we will "taint" the domain. In order for this to be fully supported (together with any future changes, which makes it easier for consumers of libvirt) it should be added to libvirt as a possibility. So you are solely relying on the fact that when we start QEMU again it will use the same paths and just resume working? That could be another reason to make changes to libvirt, if only to make sure the paths are the same.
- Michael
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