> From: Dan Williams <dan.j.williams@xxxxxxxxx> > Sent: Friday, February 1, 2019 3:47 PM > To: Dexuan Cui <decui@xxxxxxxxxxxxx> > > I believe it's the same reason. Without 11189c1089da the _LSR method > will fail, and otherwise it works and finds the label that it doesn't > like. Exactly. > I'm not seeing "invalid" data in your failure log. Could you double > check that it's just not the success of _LSR that causes the issue? acpi_label_read() never fails for me. By "invalid", I only mean the messages in the dmesg.bad.txt I previously attached (I'm just reading the specs to learn the details about NVDIMM namespace's labels, so my description might be inaccurate) : [ 4.832367] nvdimm nmem1: nsindex0 labelsize 1 invalid [ 4.832369] nvdimm nmem1: nsindex1 labelsize 1 invalid ... [ 5.259017] nd_pmem namespace0.0: 0x0000000000000000, too small must be at least 0x1000 > > > The regression you are seeing is the fact that the patch enables the kernel > to > > > enable nvdimm-namespace-label reads. > > Yes. > > > > > Those reads find a namespace index block > > > and a label. Unfortunately the label has the LOCAL flag set and Linux > > > explicitly ignores pmem namespace labels with that bit set. The reason > > Can you please point out the function that ignores the flag? > > > > I checked where NSLABEL_FLAG_LOCAL is used, but it looks I can't find a > > related function. > > scan_labels() is where the namespace label is validated relative to > the region type: > > if (is_nd_blk(&nd_region->dev) > == !!(flags & NSLABEL_FLAG_LOCAL)) > /* pass, region matches label type */; > else > continue; > > It also has meaning for the namespace capacity allocation > implementation that needed that flag to distinguish aliased capacity > between Block Aperture Mode and PMEM Mode access. Thanks for the pointer! I'm looking at this function. > > > for that is due to the fact that the original definition of the LOCAL > > > bit from v1.1 of the namespace label implementation [1] explicitly > > > limited the LOCAL flag to "block aperture" regions. If you clear that > > > LOCAL flag I expect it will work. To my knowledge Windows pretends > > > that the v1.1 definition never existed. > > I'm trying to find out where the flag is used and how to clear it. > > Assuming Hyper-V implements _LSW, you can recreate / reinitialize the > label area: I think Hyper-V only implements _LSR: [ 4.720623] nfit ACPI0012:00: device:00: has _LSR [ 4.723683] nfit ACPI0012:00: device:01: has _LSR > > > The UEFI 2.7 specification for v1.2 labels states that setting the > > > LOCAL flag is optional when "nlabel", number of labels in the set, is > > > 1. Linux makes that mandatory as LOCAL is redundant when nlabel is 1. > > > > > > That said, the Robustness Principle makes a case that Linux should > > > tolerate the bit being set. However, it's just a non-trivial amount of > > > work to unwind the ingrained block-aperture assumptions of that bit. > > Can you please explain this a bit more? Sorry, I'm new to this area... > > The short story is that Linux enforces that LOCAL == Block Mode > Namespaces. See section 2.2 Namespace Label Layout in the original > spec [1]. The EFI 2.7 definition tried to allow for LOCAL to be set > when an interleave-set was comprised of a single NVDIMM, but then also > states its optional when Nlabel is 1. It has zero functional use for > interleave-set based namespaces even when the interleave-set-width is > 1. So Linux takes the option to never set it, and goes further to > reject it if it's set and the region-type does not match, because that > follows the v1.1 meaning of the flag. > > [1]: Thanks for the link! I'll read it. BTW, it looks Hyper-V only supports PMEM namespace, at least so far. Thanks, -- Dexuan
