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Filename Latest commit message Latest commit date
James Morse ffad02f9e3 KVM: arm64: Survive synchronous exceptions caused by AT instructions
commit 88a84ccccb3966bcc3f309cdb76092a9892c0260 upstream.

KVM doesn't expect any synchronous exceptions when executing, any such
exception leads to a panic(). AT instructions access the guest page
tables, and can cause a synchronous external abort to be taken.

The arm-arm is unclear on what should happen if the guest has configured
the hardware update of the access-flag, and a memory type in TCR_EL1 that
does not support atomic operations. B2.2.6 "Possible implementation
restrictions on using atomic instructions" from DDI0487F.a lists
synchronous external abort as a possible behaviour of atomic instructions
that target memory that isn't writeback cacheable, but the page table
walker may behave differently.

Make KVM robust to synchronous exceptions caused by AT instructions.
Add a get_user() style helper for AT instructions that returns -EFAULT
if an exception was generated.

While KVM's version of the exception table mixes synchronous and
asynchronous exceptions, only one of these can occur at each location.

Re-enter the guest when the AT instructions take an exception on the
assumption the guest will take the same exception. This isn't guaranteed
to make forward progress, as the AT instructions may always walk the page
tables, but guest execution may use the translation cached in the TLB.

This isn't a problem, as since commit 5dcd0fdbb4 ("KVM: arm64: Defer guest
entry when an asynchronous exception is pending"), KVM will return to the
host to process IRQs allowing the rest of the system to keep running.

Cc: stable@vger.kernel.org # <v5.3: 5dcd0fdbb4 ("KVM: arm64: Defer guest entry when an asynchronous exception is pending")
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-09-05 11:22:50 +02:00
arch KVM: arm64: Survive synchronous exceptions caused by AT instructions 2020-09-05 11:22:50 +02:00
block blk-mq: order adding requests to hctx->dispatch and checking SCHED_RESTART 2020-09-03 11:27:01 +02:00
certs
crypto crypto: af_alg - Work around empty control messages without MSG_MORE 2020-09-03 11:27:05 +02:00
Documentation kbuild: support LLVM=1 to switch the default tools to Clang/LLVM 2020-08-26 10:40:47 +02:00
drivers drm/etnaviv: fix TS cache flushing on GPUs with BLT engine 2020-09-05 11:22:50 +02:00
fs io_uring: Fix NULL pointer dereference in io_sq_wq_submit_work() 2020-09-03 11:27:11 +02:00
include HID: core: Sanitize event code and type when mapping input 2020-09-05 11:22:49 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc
kernel kbuild: add variables for compression tools 2020-09-03 11:27:10 +02:00
lib test_kmod: avoid potential double free in trigger_config_run_type() 2020-08-21 13:05:37 +02:00
LICENSES
mm mm/vunmap: add cond_resched() in vunmap_pmd_range 2020-09-03 11:26:52 +02:00
net can: j1939: transport: j1939_xtp_rx_dat_one(): compare own packets to detect corruptions 2020-09-03 11:26:58 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts kbuild: fix broken builds because of GZIP,BZIP2,LZOP variables 2020-09-03 11:27:10 +02:00
security Smack: prevent underflow in smk_set_cipso() 2020-08-19 08:16:16 +02:00
sound ALSA: usb-audio: Update documentation comment for MS2109 quirk 2020-09-03 11:27:11 +02:00
tools perf record/stat: Explicitly call out event modifiers in the documentation 2020-09-05 11:22:49 +02:00
usr
virt KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set 2020-08-26 10:41:08 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.62 2020-09-03 11:27:11 +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.