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SubjectRE: [PATCH v2] nfit: add Hyper-V NVDIMM DSM command set to white list
Date
> From: Dan Williams <dan.j.williams@intel.com>
> Sent: Friday, February 1, 2019 5:29 PM
> > ...
> > The "size" and "mode" still don't look right, but the improvement is that
> > now I can see a good descriptive "name", which I suppose is retrieved
> > from Hyper-V.
>
> Mode is right, there is no way for Hyper-V to create Linux fsdax mode
> namespaces it requires some setup using variables only Linux knows.
> Can you send the output of:
>
> ndctl read-labels -j all

The output is from a kernel built with the libnvdimm-pending branch plus
the one-line patch (label->flags &= ~NSLABEL_FLAG_LOCAL) in
init_active_labels():

root@decui-gen2-u1904:~# ndctl read-labels -j all
[
{
"dev":"nmem1",
"index":[
{
"signature":"NAMESPACE_INDEX",
"major":1,
"minor":2,
"labelsize":256,
"seq":1,
"nslot":2
},
{
"signature":"NAMESPACE_INDEX",
"major":1,
"minor":2,
"labelsize":256,
"seq":2,
"nslot":2
}
],
"label":[
{
"uuid":"c258aaab-f72b-e546-bfa5-be5e07761dbc",
"name":"Microsoft Hyper-V NVDIMM 1 Label",
"slot":0,
"position":0,
"nlabel":1,
"isetcookie":708891662257476870,
"lbasize":0,
"dpa":0,
"rawsize":137438953472,
"type_guid":"79d3f066-f3b4-7440-ac43-0d3318b78cdb",
"abstraction_guid":"00000000-0000-0000-0000-000000000000"
}
]
},
{
"dev":"nmem0",
"index":[
{
"signature":"NAMESPACE_INDEX",
"major":1,
"minor":2,
"labelsize":256,
"seq":1,
"nslot":2
},
{
"signature":"NAMESPACE_INDEX",
"major":1,
"minor":2,
"labelsize":256,
"seq":2,
"nslot":2
}
],
"label":[
{
"uuid":"9f0497a7-4453-7c40-ad35-21a791e00345",
"name":"Microsoft Hyper-V NVDIMM 0 Label",
"slot":0,
"position":0,
"nlabel":1,
"isetcookie":708891619307803909,
"lbasize":0,
"dpa":0,
"rawsize":34359738368,
"type_guid":"79d3f066-f3b4-7440-ac43-0d3318b78cdb",
"abstraction_guid":"00000000-0000-0000-0000-000000000000"
}
]
}
]
read 2 nmems

> > With Ubuntu 19.04 (4.18.0-11-generic), I get this:
> > (Note: the "mode" and "size" are correct. The "uuid" is different from
> > the above "9f0497a7-4453-7c40-ad35-21a791e00345" -- this is weird.)
> >
> > root@decui-gen2-u1904:~# ndctl list
> > [
> > {
> > "dev":"namespace1.0",
> > "mode":"raw",
> > "size":137438953472,
> > "blockdev":"pmem1"
> > },
> > {
> > "dev":"namespace0.0",
> > "mode":"fsdax",
> > "map":"dev",
> > "size":33820770304,
> > "uuid":"35018886-397e-4fe7-a348-0a4d16eec44d",
> > "blockdev":"pmem0"
> > }
> > ]
>
> This is because the Ubuntu kernel has the bug that causes _LSR to fail
> so Linux falls back to a namespace defined by the region boundary. On
> that namespace there is an "fsdax" info block located at the region
> base +4K. That info block is tagged with the uuid of
> "35018886-397e-4fe7-a348-0a4d16eec44d".
Thanks for the explanation!

> > I'm trying to find out the correct solution. I apprecite your insights!
>
> It's a mess. First we need to figure out whether the label is actually
> specifying a size of zero, or there is some other bug.
I agree.

> However, the next problem is going to be adding "fsdax" mode support
> on top of the read-only defined namespaces. The ndctl reconfiguration
> flow:
>
> ndctl create-namespace -e namespace0.0 -m fsdax -f

>
> ...will likely fail because deleting the previous namespace in the
> labels is part of that flow. It's always that labels are writable.
>
> Honestly, the quickest path to something functional for Linux is to
> simply delete the _LSR support and use raw mode defined namespaces.
> Why have labels if they are read-only and the region is sufficient for
> defining boundaries?

Just now Hyper-V team confirmed _LSW is not supported.

But with Ubuntu 19.04 kernel (4.18.0-11-generic), I'm able to run the commands
without any issue:

root@decui-gen2-u1904:~# ndctl list
[
{
"dev":"namespace1.0",
"mode":"raw",
"size":137438953472,
"blockdev":"pmem1"
},
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"dev",
"size":33820770304,
"uuid":"35018886-397e-4fe7-a348-0a4d16eec44d",
"blockdev":"pmem0"
}
]

root@decui-gen2-u1904:~# ndctl destroy-namespace "namespace0.0"
Error: namespace0.0 is active, specify --force for re-configuration

error destroying namespaces: Device or resource busy
destroyed 0 namespaces

root@decui-gen2-u1904:~# ndctl destroy-namespace "namespace0.0" --force
destroyed 1 namespace

root@decui-gen2-u1904:~# ndctl list
[
{
"dev":"namespace1.0",
"mode":"raw",
"size":137438953472,
"blockdev":"pmem1"
}
]

root@decui-gen2-u1904:~# ndctl create-namespace -e namespace0.0 -m fsdax -f
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"dev",
"size":"31.50 GiB (33.82 GB)",
"uuid":"9e4e819b-e2eb-4796-8f9e-15f96f63b5c2",
"sector_size":512,
"blockdev":"pmem0",
"numa_node":1
}

root@decui-gen2-u1904:~# ndctl list
[
{
"dev":"namespace1.0",
"mode":"raw",
"size":137438953472,
"blockdev":"pmem1"
},
{
"dev":"namespace0.0",
"mode":"fsdax",
"map":"dev",
"size":33820770304,
"uuid":"9e4e819b-e2eb-4796-8f9e-15f96f63b5c2",
"blockdev":"pmem0"
}
]


The above commands can also run fine with an upstream kernel that
doesn't have
11189c1089da ("acpi/nfit: Fix command-supported detection")
or
1194c4133195 ("nfit: Add Hyper-V NVDIMM DSM command set to white list")

Thanks
-- Dexuan
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