On Thu, May 15, 2025 at 12:11:49PM +0200, Kevin Wolf wrote: > If you're talking about SG_IO in dm-mpath, then PRIN/PROUT commands are > actually the one thing that we don't need. libmpathpersist sends the > commands to the individual path devices, so dm-mpath will never see > those. It's mostly about getting the full results on the SCSI level for > normal I/O commands. > > There has actually been a patch series on qemu-devel last year (that I > haven't found the time to review properly yet) that would add explicit > persistent reservation operations to QEMU's block layer that could then > be used with the emulated scsi-hd device. On the backend, it only > implemented it for iscsi, but I suppose we could implement it for > file-posix, too (using the same libmpathpersist code as for > passthrough). If that works, maybe at least some users can move away > from SCSI passthrough.
Please call into the kernel PR code instead of hacking up more of this, which will just run into problems again. > The thing that we need to make sure, though, is that the emulated status > we can expose to the guest is actually good enough. That Paolo said that > the problem with reservation conflicts was mostly because -EBADE wasn't > a thing yet gives me some hope that at least this wouldn't be a problem > any more today. And if you need more information we can add that to the kernel PR API.
