| commit | f618b331bb8ad9aa76ac717bdae9db8f54165f83 | [log] [tgz] |
|---|---|---|
| author | Alexandru Elisei <alexandru.elisei@arm.com> | Fri Jan 31 16:37:22 2020 +0000 |
| committer | Andrew Jones <drjones@redhat.com> | Fri Apr 03 09:40:33 2020 +0200 |
| tree | 99c6a0181dfa2480e7ee74ee6f7e002a2bfb332d | |
| parent | 0074eebcb5f40f152b210a9ab6f5394a0ed6e065 [diff] |
arm64: timer: Add ISB before reading the counter value
Reads of the physical counter and the virtual counter registers "can occur
speculatively and out of order relative to other instructions executed on
the same PE" [1, 2].
There is no theoretical limit to the number of instructions that the CPU
can reorder and we use the counter value to program the timer to fire in
the future. Add an ISB before reading the counter to make sure the read
instruction is not reordered too long in the past with regard to the
instruction that programs the timer alarm, thus causing the timer to fire
unexpectedly. This matches what Linux does (see
arch/arm64/include/asm/arch_timer.h).
Because we use the counter value to program the timer, we create a register
dependency [3] between the value that we read and the value that we write to
CVAL and thus we don't need a barrier after the read. Linux does things
differently because the read needs to be ordered with regard to a memory
load (more information in commit 75a19a0202db ("arm64: arch_timer: Ensure
counter register reads occur with seqlock held")).
This also matches what we already do in get_cntvct from
lib/arm{,64}/asm/processor.h.
[1] ARM DDI 0487E.a, section D11.2.1
[2] ARM DDI 0487E.a, section D11.2.2
[3] ARM DDI 0486E.a, section B2.3.2
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
See http://www.linux-kvm.org/page/KVM-unit-tests for a high-level description of this project, as well as running tests and adding tests HOWTOs.
This directory contains sources for a KVM test suite.
To create the test images do:
./configure make
in this directory. Test images are created in ./ARCH/*.flat
The tests can be built as standalone. To create and use standalone tests do:
./configure make standalone (send tests/some-test somewhere) (go to somewhere) ./some-test
make install will install all tests in PREFIX/share/kvm-unit-tests/tests, each as a standalone test.
Then use the runner script to detect the correct invocation and invoke the test:
./x86-run ./x86/msr.flat
or:
./run_tests.sh
to run them all.
By default the runner script searches for a suitable QEMU binary in the system. To select a specific QEMU binary though, specify the QEMU=path/to/binary environment variable:
QEMU=/tmp/qemu/x86_64-softmmu/qemu-system-x86_64 ./x86-run ./x86/msr.flat
To select an accelerator, for example “kvm” or “tcg”, specify the ACCEL=name environment variable:
ACCEL=kvm ./x86-run ./x86/msr.flat
The test case may need specific runtime configurations, for example, extra QEMU parameters and time to execute limited, the runner script reads those information from a configuration file found at ./ARCH/unittests.cfg.
The configuration file also contain the groups (if any) each test belong to. So that a given group can be executed by specifying its name in the runner's -g option.
Unit tests use QEMU's ‘-append args...’ parameter for command line inputs, i.e. all args will be available as argv strings in main(). Additionally a file of the form
KEY=VAL KEY2=VAL ...
may be passed with ‘-initrd file’ to become the unit test's environ, which can then be accessed in the usual ways, e.g. VAL = getenv(“KEY”). Any key=val strings can be passed, but some have reserved meanings in the framework. The list of reserved environment variables is below
QEMU_ACCEL either kvm or tcg QEMU_VERSION_STRING string of the form `qemu -h | head -1` KERNEL_VERSION_STRING string of the form `uname -r`
Additionally these self-explanatory variables are reserved
QEMU_MAJOR, QEMU_MINOR, QEMU_MICRO, KERNEL_VERSION, KERNEL_PATCHLEVEL, KERNEL_SUBLEVEL, KERNEL_EXTRAVERSION
Some tests are not safe to run by default, as they may crash the host. kvm-unit-tests provides two ways to handle tests like those.
Adding ‘nodefault’ to the groups field for the unit test in the unittests.cfg file. When a unit test is in the nodefault group it is only run when invoked
a) independently, ARCH-run ARCH/test
b) by specifying any other non-nodefault group it is in, groups = nodefault,mygroup : ./run_tests.sh -g mygroup
c) by specifying all tests should be run, ./run_tests.sh -a
Making the test conditional on errata in the code,
if (ERRATA(abcdef012345)) {
do_unsafe_test();
}
With the errata condition the unsafe unit test is only run when
a) the ERRATA_abcdef012345 environment variable is provided and ‘y’
b) the ERRATA_FORCE environment variable is provided and ‘y’
c) by specifying all tests should be run, ./run_tests.sh -a (The -a switch ensures the ERRATA_FORCE is provided and set to ‘y’.)
The ./errata.txt file provides a mapping of the commits needed by errata conditionals to their respective minimum kernel versions. By default, when the user does not provide an environ, then an environ generated from the ./errata.txt file and the host's kernel version is provided to all unit tests.
.: configure script, top-level Makefile, and run_tests.sh ./scripts: helper scripts for building and running tests ./lib: general architecture neutral services for the tests ./lib/<ARCH>: architecture dependent services for the tests ./<ARCH>: the sources of the tests and the created objects/images
See ./ARCH/README for architecture specific documentation.
Currently there is a mix of indentation styles so any changes to existing files should be consistent with the existing style. For new files:
Exceptions:
Patches are welcome at the KVM mailing list kvm@vger.kernel.org.
Please prefix messages with: [kvm-unit-tests PATCH]
You can add the following to .git/config to do this automatically for you:
[format]
subjectprefix = kvm-unit-tests PATCH
Additionally it‘s helpful to have a common order of file types in patches. Our chosen order attempts to place the more declarative files before the code files. We also start with common code and finish with unit test code. git-diff’s orderFile feature allows us to specify the order in a file. The orderFile we use is scripts/git.difforder; adding the config with git config diff.orderFile scripts/git.difforder enables it.