Alright, if someone ever faces this, the label size can be the one to blame.
Judging by the manual: https://github.com/qemu/qemu/blob/master/docs/nvdimm.txt Note: 1. The minimal label size is 128KB. 2. QEMU v2.7.0 and later store labels at the end of backend storage. If a memory backend file, which was previously used as the backend of a vNVDIMM device without labels, is now used for a vNVDIMM device with label, the data in the label area at the end of file will be inaccessible to the guest. If any useful data (e.g. the meta-data of the file system) was stored there, the latter usage may result guest data corruption (e.g. breakage of guest file system). => 128KB was not enough. Changing label area to 2MB "fixed" the issue. Funny is that I'm not even trying to use labels, I'm using full regions for namespaces BUT its likely that there is a single label in those cases (being written at the end of backing files). => I was also truncating the backing files, now I'm creating full zeroed files (I guess that for the MMIO nature of DAX & PMEM, having full files is either better OR mandatory). rafaeldtinoco@ndctltest:~$ sudo ndctl disable-namespace all disabled 2 namespaces rafaeldtinoco@ndctltest:~$ sudo ndctl create-namespace -v -r region1 -m fsdax { "dev":"namespace1.0", "mode":"fsdax", "map":"dev", "size":"1006.00 MiB (1054.87 MB)", "uuid":"51dec4e0-1414-418a-9263-6459d5c12194", "sector_size":512, "align":2097152, "blockdev":"pmem1" } rafaeldtinoco@ndctltest:~$ sudo ndctl create-namespace -v -r region0 -m fsdax { "dev":"namespace0.0", "mode":"fsdax", "map":"dev", "size":"1006.00 MiB (1054.87 MB)", "uuid":"33be9543-603c-4a7f-9f2d-98a3f3ff5ec0", "sector_size":512, "align":2097152, "blockdev":"pmem0" } ** Changed in: linux (Ubuntu Focal) Status: Confirmed => Invalid ** Changed in: qemu (Ubuntu Focal) Status: Confirmed => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1855177 Title: qemu nvdimm virtualization + linux 5.3.0-24-generic kernel PROBE ERROR To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1855177/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
