RE: [ndctl PATCH v3 4/5] libndctl: Add a new dimm-op cmd_is_supported()
From: Verma, Vishal L <vishal.l.verma(a)intel.com>
Sent: Tuesday, March 26, 2019 2:56 PM
Hi Dexuan,
Thanks for making the changes, this revision /mostly/ looks good to me
except -
The kernel dsm mask just seems to be hard-coded in [1]
Yes, the kernel basically hard-codes the dsm_mask to 0x1F for Hyper-V,
but the kernel doesn't export the dsm_mask to the userspace; instead,
the kernel exports the "nvdimm->cmd_mask" to the userspace: see
drivers/nvdimm/dimm_devs.c: commands_show().
The cmd_mask is initialized in acpi_nfit_register_dimms(), and it's not
1:1 mapped to the dsm_mask for non-NVDIMM_FAMILY_INTEL families:
see acpi_nfit_register_dimms().
So is there any reason that that can't simply be allowed to
advertise
"everything is supported", similar to what the MSFT family does, and
that should remove the need for playing games with dimm-ops (i.e. now
there is another layer that can affect command support detection).
Here ndctl is checking if ND_CMD_SMART is supported in
dimm->cmd_mask. For all the non-NVDIMM_FAMILY_INTEL families,
the check is false, including the HPE1 and MSFT families.
So IMO we need this new dimm-ops to make "ndctl monitor" work
for Hyper-V. I think the other non-INTEL families can't work with
"ndctl monitor" either, but I don't have a hardward to test.
Thanks,
-- Dexuan