SCSI: Fix Persistent Reservation (PR) NVMe->SCSI conversion of HostID to Transport ID

[Alex Landau (alandau)]

Just copying it, as was done before, is wrong since HostID is 8 or 16 bytes (random-ish) and TransportID is 24 bytes (and has structure).

This change follows the T10 SPC-3 spec for the format of the TransportID retaining backward compatibility for NVMe HostIDs that start with 06 00 00 00. This last part can happen when the NVMe HostID itself is incorrectly derived from an underlying SCSI TransportID by just copying bytes.

Before:

# sg_persist --in  --read-full-status /dev/sda
  OpenVMM   Disk              1.0
  Peripheral device type: disk
  PR generation=0x1
    Key=0x1234
      All target ports bit set
      not reservation holder
      Transport Id short or not multiple of 4 [length=1024]:
        SAS address: 0xbd591cd38dc846b6

# sg_raw -r 8192 /dev/sda 5e 03 00 00 00 00 00 20 00 00 | hexdump -C
SCSI Status: Good Received 48 bytes of data:
 00     00 00 00 18 00 00 00 28  ff 00 7c 80 09 2f 6d 08    .......(..|../m.
 10     00 00 00 00 02 00 00 00  00 00 00 00 00 00 00 10    ................
 20     06 00 00 00 bd 59 1c d3  8d c8 46 b6 99 68 1d 91    .....Y....F..h..

After:

alpine:~# sg_persist --out --register --param-rk=0 --param-sark=0x1234 /dev/sda
  OpenVMM   Disk              1.0
  Peripheral device type: disk

alpine:~# sg_persist --in --read-keys /dev/sda
  OpenVMM   Disk              1.0
  Peripheral device type: disk
  PR generation=0x1, 1 registered reservation key follows:
    0x1234

alpine:~# sg_persist --in --read-full-status /dev/sda
  OpenVMM   Disk              1.0
  Peripheral device type: disk
  PR generation=0x1
    Key=0x1234
      All target ports bit set
      not reservation holder
      Transport Id of initiator:
        SAS address: 0x1020304050607

alpine:~# sg_raw -r 8192 /dev/sda 5e 03 00 00 00 00 00 20 00 00
SCSI Status: Good

Received 56 bytes of data:
 00     00 00 00 01 00 00 00 30  00 00 00 00 00 00 12 34    .......0.......4
 10     00 00 00 00 02 00 00 00  00 00 00 00 00 00 00 18    ................
 20     06 00 00 00 00 01 02 03  04 05 06 07 08 09 0a 0b    ................
 30     0c 0d 0e 0f 00 00 00 00                             ........

[Copilot]

🟡 Changes recommended

The new SAS TransportID construction currently risks populating reserved bytes for 16-byte HostIDs, which can produce a non-conformant TransportID and should be corrected before approval.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR updates SCSI Persistent Reservation (PR) “REPORT FULL STATUS” handling to correctly convert NVMe HostID values into a structured SCSI TransportID (SAS protocol identifier), rather than copying HostID bytes directly.

Changes:

• Constructs a fixed-size SAS TransportID buffer and emits it in the FULL STATUS descriptor.
• Adds a compatibility heuristic for NVMe HostIDs that appear to already contain the SAS TransportID prefix.
• Updates the descriptor’s additional_descriptor_length to match the emitted TransportID size.

File summaries

File	Description
vm/devices/storage/scsidisk/src/reservation.rs	Builds a SAS TransportID for REPORT FULL STATUS and adjusts descriptor length/output accordingly.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 2
• Review effort level: Lite

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[Copilot]

🟢 Approval recommended

The changes are small, internally consistent (length fields match emitted bytes), and the updated tests align with the corrected on-wire format.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Lite

[github-actions]

4 Petri tests failed (0 unstable)