Bug 1848887 - [ppc][nvdimm]the guest with device nvdimm specified shouldn't boot up with "nvdimm=off"
Summary: [ppc][nvdimm]the guest with device nvdimm specified shouldn't boot up with "...
Alias: None
Product: Red Hat Enterprise Linux Advanced Virtualization
Classification: Red Hat
Component: qemu-kvm
Version: 8.3
Hardware: ppc64le
OS: Linux
Target Milestone: rc
: 8.4
Assignee: Daniel Henrique Barboza
QA Contact: Min Deng
Depends On: 1718461
Blocks: 1796871
TreeView+ depends on / blocked
Reported: 2020-06-19 07:35 UTC by Min Deng
Modified: 2020-11-30 02:41 UTC (History)
14 users (show)

Fixed In Version: qemu-kvm-5.2.0-0.module+el8.4.0+8855+a9e237a9
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Type: Bug
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System ID Priority Status Summary Last Updated
IBM Linux Technology Center 188837 None None None 2020-10-23 08:12:34 UTC

Description Min Deng 2020-06-19 07:35:57 UTC
Description of problem:
[ppc][nvdimm]the guest with device nvdimm specified in cmdline shouldn't  boot up with "nvdimm=off"

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.boot up guest with 
...-machine pseries,nvdimm=off -object memory-backend-file,id=mem1,share=on,mem-path=/tmp/nvdimm1,size=1G -device nvdimm,memdev=mem1,id=nv1,label-size=512M,uuid=2b9ee44f-d390-4ad2-afd9-b84b1f31dbdf ...

Actual results:
The guest boot up successfully.

Expected results:
The guest shouldn't boot up, the guest with "-device nvdimm" specified shouldn't boot up because of "nvdimm=off",

Additional info:
Just for reference,the result was from x86.
# /usr/libexec/qemu-kvm -M pc,nvdimm=off -object memory-backend-file,id=mem0,size=1G,mem-path=/tmp/aa -device nvdimm,id=dimm0,memdev=mem0
qemu-kvm: -device nvdimm,id=dimm0,memdev=mem0: nvdimm is not enabled: missing 'nvdimm' in '-M'

Comment 1 Daniel Henrique Barboza 2020-08-28 14:07:51 UTC
I posted patches upstream for this a few days ago and forgot to
mention it here:


David accepted the fixes in his ppc-for-5.2 branch.

I wasn't able to make this option behave like other archs, specially
the behavior of disabling support by default like x86 does. The reason
is that the NVDIMM support for pSeries was released in 5.1 ignoring this
option altogether, assuming the default = enable support.

This puts the fix in a strange spot: if I change the support to be like x86,
I'll break existing pseries-5.1 users that are using NVDIMM without
specifying the 'nvdimm' option. If I leave pseries-5.1 alone and change
pseries-5.2 to be like x86, I'll change NVDIMM behavior between pseries 5.1
and 5.2, potentially breaking people doing machine updates.

What was done then is to do what we know it's reasonable to do in all
cases, and what the bug proposes: if the user explicitly puts "nvdimm=off"
in the command line, we will disable NVDIMM support regardless of the
machine version.

Comment 2 David Gibson 2020-09-21 04:26:30 UTC
Fix is now merged upstream from my last pull request, moving to POST for RHEL-AV-8.4.

Comment 4 Min Deng 2020-10-26 05:24:49 UTC
According to this piece of comment from https://bugzilla.redhat.com/show_bug.cgi?id=1718461#c20, we need this fix for rhel8.3 too, thanks.

Comment 5 David Gibson 2020-10-28 02:51:57 UTC
Subsequent comments suggest that's not necessary after all.

Comment 6 Min Deng 2020-11-30 02:41:16 UTC
Re-tested the bug, the original issue hasn't been reproduced on qemu-kvm-5.2.0-0.module+el8.4.0+8855+a9e237a9, thanks.

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