Public bug reported:
The attached screenshot of a PCIe trace snippet is from Ubuntu 20.04.3
LTS, k5.4.0-73-generic, with an NVMe controller formatted to 4K+8 DIX
PI2
It shows
- A Single-sector Write Zeroes command with SLBA=0x02E18439, ILBRT=0x0 (valid
for PI2), PRCHK=0x0 (no checks), PRACT=0 *, DEAC=0 **. Command succeeds.
- A Single-sector Read command with SLBA=0x02E18439, EILBRT=0x02E18439,
PRCHK=0x5. Command rejected with ‘End to End Ref tag Check Error’.
Using ILBRT/EILBRT=SLBA and PRCHK=0x5 is standard for PI2 Reads and Writes in
Ubuntu (so making it no different to PI1); but if Ubuntu wants to use these
values to successfully read data following a Write Zeroes command, the Write
Zeroes command should either:
a) set the PRACT bit, causing the controller to generate PI data in accordance
with the PI mode*; or
b) set the DEAC bit, causing the controller to generate standard Deallocated PI
data** (all FFs) thus disabling all checks on the next Read via the
AppTag/RefTag=0xFFFF rule.
Relevant NVMe 1.4 text:
* “If the Protection Information Action bit (PRACT) is cleared to ‘0’, then the
protection information for this command shall be all zeroes.
If the Protection Information Action bit (PRACT) is set to ‘1’, then the
protection information shall be based on the End-to-end Data Protection Type
Settings (DPS) field in the Identify Namespace data structure and the
CDW14.ILBRT, CDW15. LBATM, and CDW15. LBAT fields in the Write Zeroes command.
“
** “If the Deallocate bit is cleared to ‘0’ in a Write Zeroes command… [the
controller] shall return the protection information in that logical block based
on CDW12.PRINFO in that Write Zeroes command.
If the Deallocate bit (CDW12.DEAC) is set to ‘1’ in a Write Zeroes command…
[the controller] shall return the protection information in that logical block
as specified in section 6.7.1.1 [DSM]”
** Affects: ubuntu
Importance: Undecided
Status: New
** Tags: nvme
** Attachment added: "Screenshot of LeCroy PCIe trace"
https://bugs.launchpad.net/bugs/1947757/+attachment/5534326/+files/4k8DixPI2_Wr0s-Rd.png
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https://bugs.launchpad.net/bugs/1947757
Title:
NVMe Write Zeroes command has incorrect values for PI modes
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