Misbehaving guests can cause bus locks to degrade the performance of
a system. Non-WB (write-back) and misaligned locked RMW
(read-modify-write) instructions are referred to as "bus locks" and
require system wide synchronization among all processors to guarantee
the atomicity. The bus locks can impose notable performance penalties
for all processors within the system.
Support for the Bus Lock Threshold is indicated by CPUID
Fn8000_000A_EDX[29] BusLockThreshold=1, the VMCB provides a Bus Lock
Threshold enable bit and an unsigned 16-bit Bus Lock Threshold count.
VMCB intercept bit
VMCB Offset Bits Function
14h 5 Intercept bus lock operations
Bus lock threshold count
VMCB Offset Bits Function
120h 15:0 Bus lock counter
During VMRUN, the bus lock threshold count is fetched and stored in an
internal count register. Prior to executing a bus lock within the
guest, the processor verifies the count in the bus lock register. If
the count is greater than zero, the processor executes the bus lock,
reducing the count. However, if the count is zero, the bus lock
operation is not performed, and instead, a Bus Lock Threshold #VMEXIT
is triggered to transfer control to the Virtual Machine Monitor (VMM).
A Bus Lock Threshold #VMEXIT is reported to the VMM with VMEXIT code
0xA5h, VMEXIT_BUSLOCK. EXITINFO1 and EXITINFO2 are set to 0 on
a VMEXIT_BUSLOCK. On a #VMEXIT, the processor writes the current
value of the Bus Lock Threshold Counter to the VMCB.
More details about the Bus Lock Threshold feature can be found in AMD
APM [1].
v1 -> v2
- Incorporated misc review comments from Sean.
- Removed bus_lock_counter module parameter.
- Set the value of bus_lock_counter to zero by default and reload the value by 1
in bus lock exit handler.
- Add documentation for the behavioral difference for KVM_EXIT_BUS_LOCK.
- Improved selftest for buslock to work on SVM and VMX.
- Rewrite the commit messages.
Patches are prepared on kvm-next/next (0cdcc99eeaed)
Testing done:
- Added a selftest for the Bus Lock Threshold functionality.
- The bus lock threshold selftest has been tested on both Intel and AMD platforms.
- Tested the Bus Lock Threshold functionality on SEV and SEV-ES guests.
- Tested the Bus Lock Threshold functionality on nested guests.
v1: https://lore.kernel.org/kvm/20240709175145.9986-4-manali.shukla@amd.com/T/
[1]: AMD64 Architecture Programmer's Manual Pub. 24593, April 2024,
Vol 2, 15.14.5 Bus Lock Threshold.
https://bugzilla.kernel.org/attachment.cgi?id=306250
Manali Shukla (3):
x86/cpu: Add virt tag in /proc/cpuinfo
x86/cpufeatures: Add CPUID feature bit for the Bus Lock Threshold
KVM: X86: Add documentation about behavioral difference for
KVM_EXIT_BUS_LOCK
Nikunj A Dadhania (2):
KVM: SVM: Enable Bus lock threshold exit
KVM: selftests: Add bus lock exit test
Documentation/virt/kvm/api.rst | 5 +
arch/x86/include/asm/cpufeature.h | 1 +
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/svm.h | 5 +-
arch/x86/include/uapi/asm/svm.h | 2 +
arch/x86/kernel/cpu/mkcapflags.sh | 3 +
arch/x86/kernel/cpu/proc.c | 5 +
arch/x86/kvm/svm/nested.c | 12 ++
arch/x86/kvm/svm/svm.c | 29 ++++
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/x86_64/kvm_buslock_test.c | 130 ++++++++++++++++++
11 files changed, 193 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_buslock_test.c
base-commit: 0cdcc99eeaedf2422c80d75760293fdbb476cec1
--
2.34.1
Hi all,
This is part of a hackathon organized by LKCAMP[1], focused on writing
tests using KUnit. We reached out a while ago asking for advice on what
would be a useful contribution[2] and ended up choosing data structures
that did not yet have tests.
This patch adds tests for the llist data structure, defined in
include/linux/llist.h, and is inspired by the KUnit tests for the doubly
linked list in lib/list-test.c[3].
It is important to note that this patch depends on the patch referenced
in [4], as it utilizes the newly created lib/tests/ subdirectory.
[1] https://lkcamp.dev/about/
[2] https://lore.kernel.org/all/Zktnt7rjKryTh9-N@arch/
[3] https://elixir.bootlin.com/linux/latest/source/lib/list-test.c
[4] https://lore.kernel.org/all/20240720181025.work.002-kees@kernel.org/
---
Changes in v3:
- Resolved checkpatch warnings:
- Renamed tests for macros starting with 'for_each'
- Removed link from commit message
- Replaced hardcoded constants with ENTRIES_SIZE
- Updated initialization of llist_node array
- Fixed typos
- Update Kconfig.debug message for llist_kunit
Changes in v2:
- Add MODULE_DESCRIPTION()
- Move the tests from lib/llist_kunit.c to lib/tests/llist_kunit.c
- Change the license from "GPL v2" to "GPL"
Artur Alves (1):
lib/llist_kunit.c: add KUnit tests for llist
lib/Kconfig.debug | 11 ++
lib/tests/Makefile | 1 +
lib/tests/llist_kunit.c | 358 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 370 insertions(+)
create mode 100644 lib/tests/llist_kunit.c
--
2.46.0
The SLUB changes for 6.12 included new kunit tests that resulted in
noisy warnings, which we normally suppress, and a boot lockup in some
configurations in case the kunit tests are built-in.
The warnings are addressed in Patch 1.
The lockups I couldn't reproduce, but inspecting boot initialization
order makes me suspect the tests (which call few RCU operations) are
being executed a bit too early before RCU finishes initialization.
Moving the exection later seems to do the trick, so I'd like to ask
kunit folks to ack this change (Patch 2). If RCU folks have any
insights, it would be welcome too.
So these are now fixes for 4e1c44b3db79 ("kunit, slub: add
test_kfree_rcu() and test_leak_destroy()")
Once sent as a full patch, I also want to include comment fixes from
Ulad for kvfree_rcu_queue_batch():
https://lore.kernel.org/all/CA%2BKHdyV%3D0dpJX_v_tcuTQ-_ree-Yb9ch3F_HqfT4Yn…
The plan is to take the fixes via slab tree for a 6.12 rcX.
Signed-off-by: Vlastimil Babka <vbabka(a)suse.cz>
---
Vlastimil Babka (2):
mm, slab: suppress warnings in test_leak_destroy kunit test
kunit: move call to kunit_run_all_tests() after rcu_end_inkernel_boot()
init/main.c | 4 ++--
lib/slub_kunit.c | 4 ++--
mm/slab.h | 6 ++++++
mm/slab_common.c | 5 +++--
mm/slub.c | 5 +++--
5 files changed, 16 insertions(+), 8 deletions(-)
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20240930-b4-slub-kunit-fix-6fba4d1c1742
Best regards,
--
Vlastimil Babka <vbabka(a)suse.cz>
rxq contains a pointer to the device from where
the redirect happened. Currently, the BPF program
that was executed after a redirect via BPF_MAP_TYPE_DEVMAP*
does not have it set.
Add bugfix and related selftest.
Signed-off-by: Florian Kauer <florian.kauer(a)linutronix.de>
---
Changes in v4:
- return -> goto out_close, thanks Toke
- Link to v3: https://lore.kernel.org/r/20240909-devel-koalo-fix-ingress-ifindex-v3-0-662…
Changes in v3:
- initialize skel to NULL, thanks Stanislav
- Link to v2: https://lore.kernel.org/r/20240906-devel-koalo-fix-ingress-ifindex-v2-0-4ca…
Changes in v2:
- changed fixes tag
- added selftest
- Link to v1: https://lore.kernel.org/r/20240905-devel-koalo-fix-ingress-ifindex-v1-1-d12…
---
Florian Kauer (2):
bpf: devmap: provide rxq after redirect
bpf: selftests: send packet to devmap redirect XDP
kernel/bpf/devmap.c | 11 +-
.../selftests/bpf/prog_tests/xdp_devmap_attach.c | 114 +++++++++++++++++++--
2 files changed, 115 insertions(+), 10 deletions(-)
---
base-commit: 8e69c96df771ab469cec278edb47009351de4da6
change-id: 20240905-devel-koalo-fix-ingress-ifindex-b9293d471db6
Best regards,
--
Florian Kauer <florian.kauer(a)linutronix.de>
step_after_suspend_test fails with device busy error while
writing to /sys/power/state to start suspend. The test believes
it failed to enter suspend state with
$ sudo ./step_after_suspend_test
TAP version 13
Bail out! Failed to enter Suspend state
However, in the kernel message, I indeed see the system get
suspended and then wake up later.
[611172.033108] PM: suspend entry (s2idle)
[611172.044940] Filesystems sync: 0.006 seconds
[611172.052254] Freezing user space processes
[611172.059319] Freezing user space processes completed (elapsed 0.001 seconds)
[611172.067920] OOM killer disabled.
[611172.072465] Freezing remaining freezable tasks
[611172.080332] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[611172.089724] printk: Suspending console(s) (use no_console_suspend to debug)
[611172.117126] serial 00:03: disabled
some other hardware get reconnected
[611203.136277] OOM killer enabled.
[611203.140637] Restarting tasks ...
[611203.141135] usb 1-8.1: USB disconnect, device number 7
[611203.141755] done.
[611203.155268] random: crng reseeded on system resumption
[611203.162059] PM: suspend exit
After investigation, I noticed that for the code block
if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem"))
ksft_exit_fail_msg("Failed to enter Suspend state\n");
The write will return -1 and errno is set to 16 (device busy).
It should be caused by the write function is not successfully returned
before the system suspend and the return value get messed when waking up.
As a result, It may be better to check the time passed of those few
instructions to determine whether the suspend is executed correctly for
it is pretty hard to execute those few lines for 5 seconds.
The timer to wake up the system is set to expire after 5 seconds and
no re-arm. If the timer remaining time is 0 second and 0 nano secomd,
it means the timer expired and wake the system up. Otherwise, the system
could be considered to enter the suspend state failed if there is any
remaining time.
After appling this patch, the test would not fail for it believes the
system does not go to suspend by mistake. It now could continue to the
rest part of the test after suspend.
Fixes: bfd092b8c272 ("selftests: breakpoint: add step_after_suspend_test")
Reported-by: Sinadin Shan <sinadin.shan(a)oracle.com>
Signed-off-by: Yifei Liu <yifei.l.liu(a)oracle.com>
---
v4->v5: Remove the above quotes in the first part.
remove the incorrect format which could confuse the git.
---
.../testing/selftests/breakpoints/step_after_suspend_test.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/breakpoints/step_after_suspend_test.c b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
index dfec31fb9b30d..8d275f03e977f 100644
--- a/tools/testing/selftests/breakpoints/step_after_suspend_test.c
+++ b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
@@ -152,7 +152,10 @@ void suspend(void)
if (err < 0)
ksft_exit_fail_msg("timerfd_settime() failed\n");
- if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem"))
+ system("(echo mem > /sys/power/state) 2> /dev/null");
+
+ timerfd_gettime(timerfd, &spec);
+ if (spec.it_value.tv_sec != 0 || spec.it_value.tv_nsec != 0)
ksft_exit_fail_msg("Failed to enter Suspend state\n");
close(timerfd);
--
2.46.0