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Ard Biesheuvel f8585539df fbdev/efifb: Ignore framebuffer memmap entries that lack any memory types 
The following commit:

  38ac0287b7 ("fbdev/efifb: Honour UEFI memory map attributes when mapping the FB")

updated the EFI framebuffer code to use memory mappings for the linear
framebuffer that are permitted by the memory attributes described by the
EFI memory map for the particular region, if the framebuffer happens to
be covered by the EFI memory map (which is typically only the case for
framebuffers in shared memory). This is required since non-x86 systems
may require cacheable attributes for memory mappings that are shared
with other masters (such as GPUs), and this information cannot be
described by the Graphics Output Protocol (GOP) EFI protocol itself,
and so we rely on the EFI memory map for this.

As reported by James, this breaks some x86 systems:

  [ 1.173368] efifb: probing for efifb
  [ 1.173386] efifb: abort, cannot remap video memory 0x1d5000 @ 0xcf800000
  [ 1.173395] Trying to free nonexistent resource <00000000cf800000-00000000cf9d4bff>
  [ 1.173413] efi-framebuffer: probe of efi-framebuffer.0 failed with error -5

The problem turns out to be that the memory map entry that describes the
framebuffer has no memory attributes listed at all, and so we end up with
a mem_flags value of 0x0.

So work around this by ensuring that the memory map entry's attribute field
has a sane value before using it to mask the set of usable attributes.

Reported-by: James Hilliard <james.hilliard1@gmail.com>
Tested-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: <stable@vger.kernel.org> # v4.19+
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes: 38ac0287b7 ("fbdev/efifb: Honour UEFI memory map attributes when ...")
Link: http://lkml.kernel.org/r/20190516213159.3530-2-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-05-17 11:07:42 +02:00
arch asm-generic: kill <asm/segment.h> and improve nommu generic uaccess helpers 2019-05-16 11:26:37 -07:00
block for-5.2/block-20190507 2019-05-07 18:14:36 -07:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
Documentation media updates for v5.2-rc1 2019-05-16 11:57:16 -07:00
drivers fbdev/efifb: Ignore framebuffer memmap entries that lack any memory types 2019-05-17 11:07:42 +02:00
fs configs updates for Linux 5.2: 2019-05-16 11:46:58 -07:00
include media updates for v5.2-rc1 2019-05-16 11:57:16 -07:00
init mm: shuffle initial free memory to improve memory-side-cache utilization 2019-05-14 19:52:48 -07:00
ipc ipc: do cyclic id allocation for the ipc object. 2019-05-14 19:52:52 -07:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-16 11:00:20 -07:00
lib asm-generic: kill <asm/segment.h> and improve nommu generic uaccess helpers 2019-05-16 11:26:37 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: memcontrol: fix NUMA round-robin reclaim at intermediate level 2019-05-14 19:52:53 -07:00
net This pull consists mostly of nfsd container work: 2019-05-15 18:21:43 -07:00
samples Add gitignore file for samples/vfs/ generated files 2019-05-14 13:30:10 -07:00
scripts Kconfig updates for v5.2 2019-05-15 09:06:14 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-05-13 15:15:00 -07:00
sound ARM: SoC platform updates 2019-05-16 08:31:32 -07:00
tools Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-16 10:29:00 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt mm/mmu_notifier: convert user range->blockable to helper function 2019-05-14 09:47:49 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: add more all*.config patterns 2019-05-08 09:47:46 +09:00
.mailmap A reasonably busy cycle for docs, including: 2019-05-08 12:42:50 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS ARM: SoC-related driver updates 2019-05-16 09:19:14 -07:00
Makefile Kbuild updates for v5.2 2019-05-08 12:25:12 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.