Goal

• As a user, I want to be able to use persistent reservations in my guest. At the same time, SCSI passthrough (which is the current method to enable persistent reservations) behaves too differently from normal emulated disks, so I want to avoid it. I possibly don't even use a SCSI LUN as the backend, but another type of storage such as NVMe that can provide reservations, too. Instead of using SCSI passthrough, emulated disks should offer this functionality and use generic kernel interfaces for persistent reservations. 

Acceptance criteria

• Persistent reservations are available with scsi-hd on a host_device backend
• Windows Server Failover Cluster validation passes in a guest configured this way

Upstream status

Patches were proposed a while ago that would add support for persistent reservation commands to scsi-hd (and NVMe emulation, which we're currently not interested in). As the backend, the patches only use iscsi, so file-posix support would still have to be added.

https://patchew.org/QEMU/20241011121231.18333-1-luchangqi.123@bytedance.com/

It might be possible to pick up this work or work with the author to complete it. The first step would be reviewing what is already there.