kernel.git/arch/s390, branch linux-3.18.y

s390/smp: fix CPU hotplug deadlock with CPU rescan

2019-02-06T16:34:51Z

commit b7cb707c373094ce4008d4a6ac9b6b366ec52da5 upstream. smp_rescan_cpus() is called without the device_hotplug_lock, which can lead to a dedlock when a new CPU is found and immediately set online by a udev rule. This was observed on an older kernel version, where the cpu_hotplug_begin() loop was still present, and it resulted in hanging chcpu and systemd-udev processes. This specific deadlock will not show on current kernels. However, there may be other possible deadlocks, and since smp_rescan_cpus() can still trigger a CPU hotplug operation, the device_hotplug_lock should be held. For reference, this was the deadlock with the old cpu_hotplug_begin() loop: chcpu (rescan) systemd-udevd echo 1 > /sys/../rescan -> smp_rescan_cpus() -> (*) get_online_cpus() (increases refcount) -> smp_add_present_cpu() (new CPU found) -> register_cpu() -> device_add() -> udev "add" event triggered -----------> udev rule sets CPU online -> echo 1 > /sys/.../online -> lock_device_hotplug_sysfs() (this is missing in rescan path) -> device_online() -> (**) device_lock(new CPU dev) -> cpu_up() -> cpu_hotplug_begin() (loops until refcount == 0) -> deadlock with (*) -> bus_probe_device() -> device_attach() -> device_lock(new CPU dev) -> deadlock with (**) Fix this by taking the device_hotplug_lock in the CPU rescan path. Cc: Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman

s390/cpum_cf: Reject request for sampling in event initialization

2018-12-17T09:07:09Z

[ Upstream commit 613a41b0d16e617f46776a93b975a1eeea96417c ] On s390 command perf top fails [root@s35lp76 perf] # ./perf top -F100000 --stdio Error: cycles: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat' [root@s35lp76 perf] # Using event -e rb0000 works as designed. Event rb0000 is the event number of the sampling facility for basic sampling. During system start up the following PMUs are installed in the kernel's PMU list (from head to tail): cpum_cf --> s390 PMU counter facility device driver cpum_sf --> s390 PMU sampling facility device driver uprobe kprobe tracepoint task_clock cpu_clock Perf top executes following functions and calls perf_event_open(2) system call with different parameters many times: cmd_top --> __cmd_top --> perf_evlist__add_default --> __perf_evlist__add_default --> perf_evlist__new_cycles (creates event type:0 (HW) config 0 (CPU_CYCLES) --> perf_event_attr__set_max_precise_ip Uses perf_event_open(2) to detect correct precise_ip level. Fails 3 times on s390 which is ok. Then functions cmd_top --> __cmd_top --> perf_top__start_counters -->perf_evlist__config --> perf_can_comm_exec --> perf_probe_api This functions test support for the following events: "cycles:u", "instructions:u", "cpu-clock:u" using --> perf_do_probe_api --> perf_event_open_cloexec Test the close on exec flag support with perf_event_open(2). perf_do_probe_api returns true if the event is supported. The function returns true because event cpu-clock is supported by the PMU cpu_clock. This is achieved by many calls to perf_event_open(2). Function perf_top__start_counters now calls perf_evsel__open() for every event, which is the default event cpu_cycles (config:0) and type HARDWARE (type:0) which a predfined frequence of 4000. Given the above order of the PMU list, the PMU cpum_cf gets called first and returns 0, which indicates support for this sampling. The event is fully allocated in the function perf_event_open (file kernel/event/core.c near line 10521 and the following check fails: event = perf_event_alloc(&attr, cpu, task, group_leader, NULL, NULL, NULL, cgroup_fd); if (IS_ERR(event)) { err = PTR_ERR(event); goto err_cred; } if (is_sampling_event(event)) { if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) { err = -EOPNOTSUPP; goto err_alloc; } } The check for the interrupt capabilities fails and the system call perf_event_open() returns -EOPNOTSUPP (-95). Add a check to return -ENODEV when sampling is requested in PMU cpum_cf. This allows common kernel code in the perf_event_open() system call to test the next PMU in above list. Fixes: 97b1198fece0 (" "s390, perf: Use common PMU interrupt disabled code") Signed-off-by: Thomas Richter Reviewed-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky Signed-off-by: Sasha Levin

s390/vdso: add missing FORCE to build targets

2018-11-27T15:05:36Z

[ Upstream commit b44b136a3773d8a9c7853f8df716bd1483613cbb ] According to Documentation/kbuild/makefiles.txt all build targets using if_changed should use FORCE as well. Add missing FORCE to make sure vdso targets are rebuild properly when not just immediate prerequisites have changed but also when build command differs. Reviewed-by: Philipp Rudo Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky Signed-off-by: Sasha Levin

s390/ftrace/jprobes: Fix conflict between jprobes and function graph tracing

2018-11-10T15:39:13Z

[ Upstream commit e64a5470dcd2900ab8f8f83638c00098b10e6300 ] This fixes the same issue Steven already fixed for x86 in following commit: 237d28db036e ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing It fixes the crash, that happens when function graph tracing and jprobes are used simultaneously. Please refer to above commit for details. Signed-off-by: Jiri Olsa Signed-off-by: Martin Schwidefsky Acked-by: Steven Rostedt Signed-off-by: Sasha Levin

s390/kvm: REPLACE barrier fixup with READ_ONCE

2018-11-10T15:39:13Z

[ Upstream commit 5de72a2247ac05bde7c89039631b3d0c6186fafb ] ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Commit 1365039d0cb3 ("KVM: s390: Fix ipte locking") replace ACCESS_ONCE with barriers. Lets use READ_ONCE instead. Signed-off-by: Christian Borntraeger Acked-by: Paul E. McKenney Signed-off-by: Sasha Levin

s390/extmem: fix gcc 8 stringop-overflow warning

2018-10-13T07:09:25Z

[ Upstream commit 6b2ddf33baec23dace85bd647e3fc4ac070963e8 ] arch/s390/mm/extmem.c: In function '__segment_load': arch/s390/mm/extmem.c:436:2: warning: 'strncat' specified bound 7 equals source length [-Wstringop-overflow=] strncat(seg->res_name, " (DCSS)", 7); What gcc complains about here is the misuse of strncat function, which in this case does not limit a number of bytes taken from "src", so it is in the end the same as strcat(seg->res_name, " (DCSS)"); Keeping in mind that a res_name is 15 bytes, strncat in this case would overflow the buffer and write 0 into alignment byte between the fields in the struct. To avoid that increasing res_name size to 16, and reusing strlcat. Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

s390/pci: fix out of bounds access during irq setup

2018-09-05T07:16:23Z

commit 866f3576a72b2233a76dffb80290f8086dc49e17 upstream. During interrupt setup we allocate interrupt vectors, walk the list of msi descriptors, and fill in the message data. Requesting more interrupts than supported on s390 can lead to an out of bounds access. When we restrict the number of interrupts we should also stop walking the msi list after all supported interrupts are handled. Cc: stable@vger.kernel.org Signed-off-by: Sebastian Ott Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman

s390/qdio: reset old sbal_state flags

2018-09-05T07:16:23Z

commit 64e03ff72623b8c2ea89ca3cb660094e019ed4ae upstream. When allocating a new AOB fails, handle_outbound() is still capable of transmitting the selected buffer (just without async completion). But if a previous transfer on this queue slot used async completion, its sbal_state flags field is still set to QDIO_OUTBUF_STATE_FLAG_PENDING. So when the upper layer driver sees this stale flag, it expects an async completion that never happens. Fix this by unconditionally clearing the flags field. Fixes: 104ea556ee7f ("qdio: support asynchronous delivery of storage blocks") Cc: #v3.2+ Signed-off-by: Julian Wiedmann Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman

s390/kvm: fix deadlock when killed by oom

2018-09-05T07:16:22Z

commit 306d6c49ac9ded11114cb53b0925da52f2c2ada1 upstream. When the oom killer kills a userspace process in the page fault handler while in guest context, the fault handler fails to release the mm_sem if the FAULT_FLAG_RETRY_NOWAIT option is set. This leads to a deadlock when tearing down the mm when the process terminates. This bug can only happen when pfault is enabled, so only KVM clients are affected. The problem arises in the rare cases in which handle_mm_fault does not release the mm_sem. This patch fixes the issue by manually releasing the mm_sem when needed. Fixes: 24eb3a824c4f3 ("KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault") Cc: # 3.15+ Signed-off-by: Claudio Imbrenda Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman

perf: fix invalid bit in diagnostic entry

2018-08-09T10:20:29Z

[ Upstream commit 3c0a83b14ea71fef5ccc93a3bd2de5f892be3194 ] The s390 CPU measurement facility sampling mode supports basic entries and diagnostic entries. Each entry has a valid bit to indicate the status of the entry as valid or invalid. This bit is bit 31 in the diagnostic entry, but the bit mask definition refers to bit 30. Fix this by making the reserved field one bit larger. Fixes: 7e75fc3ff4cf ("s390/cpum_sf: Add raw data sampling to support the diagnostic-sampling function") Signed-off-by: Thomas Richter Reviewed-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman