[REGRESSION] firmware: dmi_scan: add SBMIOS entry and DMI tables

From	Paul Menzel <paulepanter@users.sourceforge.net>
Newsgroups	linux.kernel
Subject	[REGRESSION] firmware: dmi_scan: add SBMIOS entry and DMI tables
Date	2016-03-28 11:30 +0200
Message-ID	<rhBEK-4UD-9@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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Dear Ivan, dear Jeann,


There is an unwanted regression due to commit d7f96f97 (firmware:
dmi_scan: add SBMIOS entry and DMI tables).

Since Linux kernel 4.2 the utility `cbmem`, used to access information
stored in memory, from the coreboot project [1] does not work anymore
on a lot of systems as reported in coreboot’s issue tracker as ticket
#33 [2].

```
Failed to mmap /dev/mem: Resource temporarily unavailable
```

Aaron Durbin analyzed on the coreboot mailing list [3]:

> > 3) Why is that range set as uncached-minus?  Would write-back work?
>
> Please see this thread:
> http://www.coreboot.org/pipermail/coreboot/2015-September/080381.html
>
> The actual issue stems from
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/firmware/dmi_scan.c?id=d7f96f97c4031fa4ffdb7801f9aae23e96170a6f
> which maintains a persistent mapping of smbios tables. It uses
> dmi_remap() which is '#define dmi_remap ioremap' which is where the
> uncached-minus PAT entry comes from. It should be using the same
> mechanism as  the ACPI table mappings which uses ioremap_cache().

It’d be great, if the commit could be reverted, or the code be changed
in a way that `cbmem` still works.

If I should report this issue somewhere else, please tell me too, and
I’ll do my best to follow up there.


Thanks,

Paul


[1] https://www.coreboot.org
[2] https://ticket.coreboot.org/issues/33
[3] https://www.coreboot.org/pipermail/coreboot/2015-October/080568.html

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[REGRESSION] firmware: dmi_scan: add SBMIOS entry and DMI tables Paul Menzel <paulepanter@users.sourceforge.net> - 2016-03-28 11:30 +0200
  Re: [REGRESSION] firmware: dmi_scan: add SBMIOS entry and DMI tables "ivan.khoronzhuk" <ivan.khoronzhuk@linaro.org> - 2016-03-28 14:50 +0200
    Re: [REGRESSION] firmware: dmi_scan: add SBMIOS entry and DMI tables Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> - 2016-03-28 15:20 +0200

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