Messages in this thread | | | From | Dexuan Cui <> | Subject | RE: [PATCH] libnvdimm/dimm: Add a no-BLK quirk based on NVDIMM family | Date | Sun, 3 Feb 2019 18:13:35 +0000 |
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> From: Dan Williams <dan.j.williams@intel.com> > Sent: Sunday, February 3, 2019 9:49 AM > > ... > > It looks the namespace created by Ubuntu 19.04 (4.18) is incompatible with > > the libnvdimm-pending branch + this patch. > > This is correct, the configuration switched from label-less by default > to labeled. Thanks for the confirmation!
> > It looks we need to completely disable the label usage for > NVDIMM_FAMILY_HYPERV > > due to compability? > > It's either going to be a quirk in Linux or a quirk in the Hyper-V > configuration. I think it's more manageable for Hyper-V to ship a > "label disable" switch than to try to ship a workaround in Linux. The > "noblk" quirk in Linux works around the LOCAL bit in the labels. > However, the namespace mode regression can only be resolved by hiding > the label capability until the administrator manually switches from > label-less to labeled operation.
As I understand, the essence of the issue is: Hyper-V emulates the label mechanism (i.e. it supports _LSI and LSR), but doesn't do it right (i.e. it doesn't support _LSW).
To manage the namespaces, Linux can choose to use label or not.
If _LSI/_LSR are supported, Linux assumes _LSW is supported as well and chooses to use label (i.e. the label mode), but since Hyper-V doesn't support _LSW, Linux fails to change the namespace configuration. In Ubuntu 19.04 (4.18), the kernel is not aware of Hyper-V _LSI/_LSR, so the created namespace is in "label-less" mode, and hence can't be used with the libnvdimm-pending branch + this patch, unless we add a quirk in Linux to explicitly not use the label.
I agree ideally Hyper-V should hide the label capability, and I'll request Hyper-V team to do that. I hope Hyper-V guys are still able to do that in time so we won't need a quirk in Linux kernel.
BTW, I suppose Windows VM should be in "label-less" mode.
Thanks for the help, Dan!
Thanks, -- Dexuan
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