[coreboot] cbmem fails with `Failed to mmap /dev/mem: Resource temporarily unavailable`

[Paul Menzel]

Dear Aaron,


thank you for the quick reply.


Am Montag, den 28.09.2015, 09:38 -0500 schrieb Aaron Durbin:
> On Sun, Sep 27, 2015 at 2:54 PM, Paul Menzel wrote:

> > building a coreboot image for the ASRock E350M1 with the attached
> > config, having code coverage enabled, I am unable to run the 
> > utility `cbmem`.
> > 
> > ```
> > $ sudo util/cbmem/cbmem -V -l
> > Looking for coreboot table at 0 1048576 bytes.
> > Mapping 1MB of physical memory at 0x0 (requested 0x0).
> > Found!
> >   coreboot table entry 0x11
> >     Found forwarding entry.
> > Unmapping 1MB of virtual memory at 0xb74b6000.
> > Looking for coreboot table at c7f9f000 1048576 bytes.
> > Mapping 1MB of physical memory at 0xffffffffc7f9f000 (requested 0xc7f9f000).
> >   ... failed.  Mapping 1052671B of physical memory at 0xffffffffc7f9e000.
> > Failed to mmap /dev/mem: Resource temporarily unavailable
> > ```
> > 
> > Linux complains with the messages below.
> > 
> > ```
> > $ dmesg
> > […]
> > [  916.233910] x86/PAT: cbmem:2647 conflicting memory types c7f9f000-c809f000 uncached-minus<->write-back
> > [  916.233927] x86/PAT: reserve_memtype failed [mem 0xc7f9f000-0xc809efff], track uncached-minus, req write-back
> > […]
> > ```
> > 
> 
> You are going to need to open the /dev/mem file w/ O_SYNC flags
> because the kernel is marking that range of memory as uncacheable.
> More info can be found here:
> https://www.kernel.org/doc/Documentation/x86/pat.txt

I totally missed, that besides selecting code coverage, the Linux
kernel was updated to version 4.2 in between. Probably they changed
some default.

    $ uname -a
    Linux my-asrocke350m1 4.2.0-1-686-pae #1 SMP Debian 4.2.1-1 (2015-09-25) i686 GNU/Linux

> # cat /sys/kernel/debug/x86/pat_memtype_list
> 
> would be helpful

    $ sudo more /sys/kernel/debug/x86/pat_memtype_list 
    PAT memtype list:
uncached-minus @ 0xc7fa7000-0xc7fa8000
write-back @ 0xc7fb8000-0xc7fbb000
write-back @ 0xc7fba000-0xc7fbd000
write-combining @ 0xe0040000-0xe0274000
write-combining @ 0xe0274000-0xe0474000
write-combining @ 0xe0474000-0xe0475000
write-combining @ 0xe0478000-0xe0978000
uncached-minus @ 0xf0004000-0xf0005000
uncached-minus @ 0xf0100000-0xf0140000
uncached-minus @ 0xf0140000-0xf0144000
uncached-minus @ 0xf0144000-0xf0148000
uncached-minus @ 0xf0148000-0xf0149000
uncached-minus @ 0xf0149000-0xf014a000
uncached-minus @ 0xf014a000-0xf014b000
uncached-minus @ 0xf014b000-0xf014c000
uncached-minus @ 0xf014b000-0xf014c000
uncached-minus @ 0xf014b000-0xf014c000
uncached-minus @ 0xf014b000-0xf014c000
uncached-minus @ 0xf8088000-0xf8089000
uncached-minus @ 0xfed00000-0xfed01000
uncached-minus @ 0xfed80000-0xfed81000

> along with this:
> 
> $ for i in /sys/firmware/memmap/*; do echo $(cat $i/type $i/start $i/end); done

    $ for i in /sys/firmware/memmap/*; do echo $(sudo cat $i/type $i/start $i/end); done
    System RAM 0x0 0x9fbff
    reserved 0x9fc00 0x9ffff
    reserved 0xf0000 0xfffff
    System RAM 0x100000 0xc7f9cfff
    reserved 0xc7f9d000 0xdfffffff
    reserved 0xf8000000 0xfbffffff
    System RAM 0x100000000 0x21effffff


Thanks,

Paul
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