Re: [PATCH 0/2] NVMe namespace hotplug and drive reconnection support

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Apr 13, 2026 at 07:17:37PM +0200, Klaus Jensen wrote:
> On Apr  9 08:01, mr-083 wrote:
> > This series adds two features that together enable transparent NVMe disk
> > hot-swap simulation in QEMU, matching the behavior of physical NVMe
> > drives being pulled and reinserted in the same PCIe slot.
> > 
> 
> I don't understand this. From an NVMe perspective you can't hotplug a
> namespace. You can hotplug a PCIe-based NVM Subsystem.

Hi Klaus,
It would be great if someone with more NVMe experience than myself can
find a definite answer, but I think the Namespace List can change
asynchronously even on a NVMe PCIe controller as long as it supports
Namespace Management commands.

There are instances in the NVMe Express Base Specification 2.0b like:
- 8.3.1 Capacity Management Overview
  "a Namespace Attribute Changed event is generated for hosts other than
  the host which issued the Capacity Management command"
- 8.11 Namespace Management
  "If Namespace Attribute Notices are enabled, any controller(s) not
  processing the Namespace Management command that was attached to the
  namespace reports a Namespace Attribute Changed asynchronous event to
  the host."

I imagine this functionality would be useful in storage offload cards
(IPUs/DPUs) that present as NVMe PCIe controllers instead of as
NVMe-over-Fabrics. This makes sense when the host is not supposed to
manage the storage itself. When the card's control plane configures a
new volume, the NVMe Namespace List changes and the host is notified.

Linux and Windows NVMe PCI drivers support this according to the testing
that Matthieu and I have done.

Thanks,
Stefan

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