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Filename Latest commit message Latest commit date
Borislav Petkov 5683ed468f x86/Kconfig: Do not enable AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT automatically
commit 711885906b5c2df90746a51f4cd674f1ab9fbb1d upstream.

This Kconfig option was added initially so that memory encryption is
enabled by default on machines which support it.

However, devices which have DMA masks that are less than the bit
position of the encryption bit, aka C-bit, require the use of an IOMMU
or the use of SWIOTLB.

If the IOMMU is disabled or in passthrough mode, the kernel would switch
to SWIOTLB bounce-buffering for those transfers.

In order to avoid that,

  2cc13bb4f5 ("iommu: Disable passthrough mode when SME is active")

disables the default IOMMU passthrough mode so that devices for which the
default 256K DMA is insufficient, can use the IOMMU instead.

However 2, there are cases where the IOMMU is disabled in the BIOS, etc.
(think the usual hardware folk "oops, I dropped the ball there" cases) or a
driver doesn't properly use the DMA APIs or a device has a firmware or
hardware bug, e.g.:

  ea68573d408f ("drm/amdgpu: Fail to load on RAVEN if SME is active")

However 3, in the above GPU use case, there are APIs like Vulkan and
some OpenGL/OpenCL extensions which are under the assumption that
user-allocated memory can be passed in to the kernel driver and both the
GPU and CPU can do coherent and concurrent access to the same memory.
That cannot work with SWIOTLB bounce buffers, of course.

So, in order for those devices to function, drop the "default y" for the
SME by default active option so that users who want to have SME enabled,
will need to either enable it in their config or use "mem_encrypt=on" on
the kernel command line.

 [ tlendacky: Generalize commit message. ]

Fixes: 7744ccdbc1 ("x86/mm: Add Secure Memory Encryption (SME) support")
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/8bbacd0e-4580-3194-19d2-a0ecad7df09c@molgen.mpg.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-20 11:40:15 +02:00
arch x86/Kconfig: Do not enable AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT automatically 2021-10-20 11:40:15 +02:00
block Revert "block, bfq: honor already-setup queue merges" 2021-10-06 15:42:34 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation dt-bindings: mtd: gpmc: Fix the ECC bytes vs. OOB bytes equation 2021-09-22 12:26:43 +02:00
drivers nvmem: Fix shift-out-of-bound (UBSAN) with byte size cells 2021-10-20 11:40:14 +02:00
fs btrfs: check for error when looking up inode during dir entry replay 2021-10-20 11:40:13 +02:00
include sched: Always inline is_percpu_thread() 2021-10-17 10:42:34 +02:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc
kernel bpf: Fix integer overflow in prealloc_elems_and_freelist() 2021-10-13 10:08:18 +02:00
lib Kconfig.debug: drop selecting non-existing HARDLOCKUP_DETECTOR_ARCH 2021-09-26 14:07:10 +02:00
LICENSES
mm mm/memory_hotplug: use "unsigned long" for PFN in zone_for_pfn_range() 2021-09-22 12:26:43 +02:00
net mac80211: check return value of rhashtable_init 2021-10-17 10:42:34 +02:00
samples samples: bpf: Fix tracex7 error raised on the missing argument 2021-09-22 12:26:30 +02:00
scripts nds32/ftrace: Fix Error: invalid operands (*UND* and *UND* sections) for `^' 2021-10-20 11:40:12 +02:00
security apparmor: remove duplicate macro list_entry_is_head() 2021-09-26 14:07:06 +02:00
sound ALSA: hda/realtek: Fix the mic type detection issue for ASUS G551JW 2021-10-20 11:40:12 +02:00
tools tools/vm/page-types: remove dependency on opt_file for idle page tracking 2021-10-09 14:39:50 +02:00
usr
virt KVM: do not shrink halt_poll_ns below grow_start 2021-10-09 14:39:50 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.154 2021-10-17 10:42:35 +02:00
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.