[PVE-User] Dell PowerEdge T140, megaraid, BIOS Boot...

[Marco Gaiarin]

I've just upgraded to PVE8 a little cluster built with an PowerEdge T340
(boot in UEFI mode) and an T140 (boot in BIOS mode).

T340 works like a charme; T140 after rebooting panicked because cannot find
root filesystem; looking carefully at kernel log revealed that disks get not
recognized, and going deeper lead me to:

 gaio at leia:~$ grep megaraid T140_boot_log.txt
 [   31.952470] megaraid_sas 0000:01:00.0: FW now in Ready state
 [   31.952472] megaraid_sas 0000:01:00.0: 63 bit DMA mask and 32 bit consistent mask
 [   31.952624] megaraid_sas 0000:01:00.0: firmware supports msix        : (96)
 [   31.952750] megaraid_sas 0000:01:00.0: requested/available msix 5/5 poll_queue 0
 [   31.952752] megaraid_sas 0000:01:00.0: current msix/online cpus      : (5/4)
 [   31.952753] megaraid_sas 0000:01:00.0: RDPQ mode     : (disabled)
 [   31.952758] megaraid_sas 0000:01:00.0: Current firmware supports maximum commands: 928        LDIO threshold: 237
 [   31.954076] megaraid_sas 0000:01:00.0: Performance mode :Latency (latency index = 1)
 [   31.954078] megaraid_sas 0000:01:00.0: FW supports sync cache        : No
 [   31.954080] megaraid_sas 0000:01:00.0: megasas_disable_intr_fusion is called outbound_intr_mask:0x40000009
 [   32.362294] megaraid_sas 0000:01:00.0: Ignore DCMD timeout: megasas_get_ctrl_info 5382
 [   32.665126] megaraid_sas 0000:01:00.0: Could not get controller info. Fail from megasas_init_adapter_fusion 1907
 [   32.908139] megaraid_sas 0000:01:00.0: Failed from megasas_init_fw 6539

googling a bit lead me to some forum and pages; after some test i've added
to kernel boot parameters:

	iommu=pt

and now server boot flawlessy.


The two servers have different hardware but share the same BIOS, so this
lead to me to the hypotesis that the new megaraid_sas kernel driver depend
on UEFI initialization to work, or something like this.

Also, i've understood that 'pt' mean 'PassThrought', but i've not clear what
overral consequences (performance, stability, ...) have this options.


I'm seeking feedback. Thanks.

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