ACPI: NFIT: Fix support for virtual SPA ranges

Fix the NFIT parsing code to treat a 0 index in a SPA Range Structure as
a special case and not match Region Mapping Structures that use 0 to
indicate that they are not mapped. Without this fix some platform BIOS
descriptions of "virtual disk" ranges do not result in the pmem driver
attaching to the range.

Details:
In addition to typical persistent memory ranges, the ACPI NFIT may also
convey "virtual" ranges. These ranges are indicated by a UUID in the SPA
Range Structure of UUID_VOLATILE_VIRTUAL_DISK, UUID_VOLATILE_VIRTUAL_CD,
UUID_PERSISTENT_VIRTUAL_DISK, or UUID_PERSISTENT_VIRTUAL_CD. The
critical difference between virtual ranges and UUID_PERSISTENT_MEMORY, is
that virtual do not support associations with Region Mapping Structures.
For this reason the "index" value of virtual SPA Range Structures is
allowed to be 0. If a platform BIOS decides to represent unmapped
NVDIMMs with a 0 index in their "SPA Range Structure Index" the driver
falsely matches them and may falsely require labels where "virtual
disks" are expected to be label-less. I.e. label-less is where the
namespace-range == region-range and the pmem driver attaches with no
user action to create a namespace.

Cc: Jacek Zloch <jacek.zloch@intel.com>
Cc: Lukasz Sobieraj <lukasz.sobieraj@intel.com>
Cc: "Lee, Chun-Yi" <jlee@suse.com>
Cc: <stable@vger.kernel.org>
Fixes: c2f32acdf848 ("acpi, nfit: treat virtual ramdisk SPA as pmem region")
Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Reported-by: Damian Bassa <damian.bassa@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/acpi/nfit/core.c |    2 ++
 1 file changed, 2 insertions(+)

Dan Williams <dan.j.williams@intel.com> writes:

> Fix the NFIT parsing code to treat a 0 index in a SPA Range Structure as

> a special case and not match Region Mapping Structures that use 0 to

> indicate that they are not mapped. Without this fix some platform BIOS

> descriptions of "virtual disk" ranges do not result in the pmem driver

> attaching to the range.

>

> Details:

> In addition to typical persistent memory ranges, the ACPI NFIT may also

> convey "virtual" ranges. These ranges are indicated by a UUID in the SPA

> Range Structure of UUID_VOLATILE_VIRTUAL_DISK, UUID_VOLATILE_VIRTUAL_CD,

> UUID_PERSISTENT_VIRTUAL_DISK, or UUID_PERSISTENT_VIRTUAL_CD. The

> critical difference between virtual ranges and UUID_PERSISTENT_MEMORY, is

> that virtual do not support associations with Region Mapping Structures.

> For this reason the "index" value of virtual SPA Range Structures is

> allowed to be 0. If a platform BIOS decides to represent unmapped

                                                           ^^^^^^^^
> NVDIMMs with a 0 index in their "SPA Range Structure Index" the driver

  ^^^^^^^

That language confused me.  I thought you were talking about a separate
issue, whereby NVDIMMs which are not mapped (probably due to some errors
with the dimms themselves) would get an index of 0.  But upon
re-reading, I think you just meant that the virtual media is not mapped
via a region mapping structure.

> falsely matches them and may falsely require labels where "virtual

> disks" are expected to be label-less. I.e. label-less is where the

> namespace-range == region-range and the pmem driver attaches with no

> user action to create a namespace.



> Cc: Jacek Zloch <jacek.zloch@intel.com>

> Cc: Lukasz Sobieraj <lukasz.sobieraj@intel.com>

> Cc: "Lee, Chun-Yi" <jlee@suse.com>

> Cc: <stable@vger.kernel.org>

> Fixes: c2f32acdf848 ("acpi, nfit: treat virtual ramdisk SPA as pmem region")

> Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>

> Reported-by: Damian Bassa <damian.bassa@intel.com>

> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

> ---

>  drivers/acpi/nfit/core.c |    2 ++

>  1 file changed, 2 insertions(+)

>

> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c

> index 23d9a09d7060..6f15e56ef955 100644

> --- a/drivers/acpi/nfit/core.c

> +++ b/drivers/acpi/nfit/core.c

> @@ -3021,6 +3021,8 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc,

>  		struct acpi_nfit_memory_map *memdev = nfit_memdev->memdev;

>  		struct nd_mapping_desc *mapping;

>  

> +		if (memdev->range_index == 0 || spa->range_index == 0)

> +			continue;

>  		if (memdev->range_index != spa->range_index)

>  			continue;

>  		if (count >= ND_MAX_MAPPINGS) {


The change looks good, but can you add a comment to the code?  With
that, you can add my:

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>


Thanks!
Jeff