- 24 Apr, 2017 9 commits
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David Gibson authored
powerpc expects IRQs to already be (soft) disabled when switch_mm() is called, as made clear in the commit message of 9c1e1052 ("powerpc: Allow perf_counters to access user memory at interrupt time"). Aside from any race conditions that might exist between switch_mm() and an IRQ, there is also an unconditional hard_irq_disable() in switch_slb(). If that isn't followed at some point by an IRQ enable then interrupts will remain disabled until we return to userspace. It is true that when switch_mm() is called from the scheduler IRQs are off, but not when it's called by use_mm(). Looking closer we see that last year in commit f98db601 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler") this was made more explicit by the addition of switch_mm_irqs_off() which is now called by the scheduler, vs switch_mm() which is used by use_mm(). Arguably it is a bug in use_mm() to call switch_mm() in a different context than it expects, but fixing that will take time. This was discovered recently when vhost started throwing warnings such as: BUG: sleeping function called from invalid context at kernel/mutex.c:578 in_atomic(): 0, irqs_disabled(): 1, pid: 10768, name: vhost-10760 no locks held by vhost-10760/10768. irq event stamp: 10 hardirqs last enabled at (9): _raw_spin_unlock_irq+0x40/0x80 hardirqs last disabled at (10): switch_slb+0x2e4/0x490 softirqs last enabled at (0): copy_process+0x5e8/0x1260 softirqs last disabled at (0): (null) Call Trace: show_stack+0x88/0x390 (unreliable) dump_stack+0x30/0x44 __might_sleep+0x1c4/0x2d0 mutex_lock_nested+0x74/0x5c0 cgroup_attach_task_all+0x5c/0x180 vhost_attach_cgroups_work+0x58/0x80 [vhost] vhost_worker+0x24c/0x3d0 [vhost] kthread+0xec/0x100 ret_from_kernel_thread+0x5c/0xd4 Prior to commit 04b96e55 ("vhost: lockless enqueuing") (Aug 2016) the vhost_worker() would do a spin_unlock_irq() not long after calling use_mm(), which had the effect of reenabling IRQs. Since that commit removed the locking in vhost_worker() the body of the vhost_worker() loop now runs with interrupts off causing the warnings. This patch addresses the problem by making the powerpc code mirror the x86 code, ie. we disable interrupts in switch_mm(), and optimise the scheduler case by defining switch_mm_irqs_off(). Cc: stable@vger.kernel.org # v4.7+ Signed-off-by:
David Gibson <david@gibson.dropbear.id.au> [mpe: Flesh out/rewrite change log, add stable] Signed-off-by:
Michael Ellerman <mpe@ellerman.id.au>
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Tyrel Datwyler authored
For CPUs present at boot each logical CPU acquires a reference to the associated device node of the core. This happens in register_cpu() which is called by topology_init(). The result of this is that we end up with a reference held by each thread of the core. However, these references are never freed if the CPU core is DLPAR removed. This patch fixes the reference leaks by acquiring and releasing the references in the CPU hotplug callbacks un/register_cpu_online(). With this patch symmetric reference counting is observed with both CPUs present at boot, and those DLPAR added after boot. Fixes: f86e4718 ("driver/core: cpu: initialize of_node in cpu's device struture") Cc: stable@vger.kernel.org # v3.12+ Signed-off-by:
Tyrel Datwyler <tyreld@linux.vnet.ibm.com> Signed-off-by:
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Tyrel Datwyler authored
Historically struct device_node references were tracked using a kref embedded as a struct field. Commit 75b57ecf ("of: Make device nodes kobjects so they show up in sysfs") (Mar 2014) refactored device_nodes to be kobjects such that the device tree could by more simply exposed to userspace using sysfs. Commit 0829f6d1 ("of: device_node kobject lifecycle fixes") (Mar 2014) followed up these changes to better control the kobject lifecycle and in particular the referecne counting via of_node_get(), of_node_put(), and of_node_init(). A result of this second commit was that it introduced an of_node_put() call when a dynamic node is detached, in of_node_remove(), that removes the initial kobj reference created by of_node_init(). Traditionally as the original dynamic device node user the pseries code had assumed responsibilty for releasing this final reference in its platform specific DLPAR detach code. This patch fixes a refcount underflow introduced by commit 0829f6d1, and recently exposed by the upstreaming of the recount API. Messages like the following are no longer seen in the kernel log with this patch following DLPAR remove operations of cpus and pci devices. rpadlpar_io: slot PHB 72 removed refcount_t: underflow; use-after-free. ------------[ cut here ]------------ WARNING: CPU: 5 PID: 3335 at lib/refcount.c:128 refcount_sub_and_test+0xf4/0x110 Fixes: 0829f6d1 ("of: device_node kobject lifecycle fixes") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by:
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Michael Ellerman authored
Currently the code that dumps SLB entries uses a double-nested if. This means the actual dumping logic is a bit squashed. Deindent it by using continue. Signed-off-by:
Rashmica Gupta <rashmica.g@gmail.com> Signed-off-by:
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Michael Ellerman authored
Although most of these kprobes patches are powerpc specific, there's a couple that touch generic code (with Acks). At the moment there's one conflict with acme's tree, but it's not too bad. Still just in case some other conflicts show up, we've put these in a topic branch so another tree could merge some or all of it if necessary.
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Naveen N. Rao authored
KPROBES_ON_FTRACE avoids much of the overhead of regular kprobes as it eliminates the need for a trap, as well as the need to emulate or single-step instructions. Though OPTPROBES provides us with similar performance, we have limited optprobes trampoline slots. As such, when asked to probe at a function entry, default to using the ftrace infrastructure. With: # cd /sys/kernel/debug/tracing # echo 'p _do_fork' > kprobe_events before patch: # cat ../kprobes/list c0000000000daf08 k _do_fork+0x8 [DISABLED] c000000000044fc0 k kretprobe_trampoline+0x0 [OPTIMIZED] and after patch: # cat ../kprobes/list c0000000000d074c k _do_fork+0xc [DISABLED][FTRACE] c0000000000412b0 k kretprobe_trampoline+0x0 [OPTIMIZED] Signed-off-by:
Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by:
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Naveen N. Rao authored
kprobe_lookup_name() is specific to the kprobe subsystem and may not always return the function entry point (in a subsequent patch for KPROBES_ON_FTRACE). For looking up function entry points, introduce a separate helper and use it in optprobes.c Signed-off-by:
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Naveen N. Rao authored
Allow kprobes to be placed on ftrace _mcount() call sites. This optimization avoids the use of a trap, by riding on ftrace infrastructure. This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS which depends on MPROFILE_KERNEL, which is only currently enabled on powerpc64le with newer toolchains. Based on the x86 code by Masami. Signed-off-by:
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Naveen N. Rao authored
Pass the real LR to the ftrace handler. This is needed for KPROBES_ON_FTRACE for the pre handlers. Also, with KPROBES_ON_FTRACE, the link register may be updated by the pre handlers or by a registed kretprobe. Honor updated LR by restoring it from pt_regs, rather than from the stack save area. Live patch and function graph continue to work fine with this change. Signed-off-by:
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- 23 Apr, 2017 14 commits
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Naveen N. Rao authored
Blacklist all the exception common/OOL handlers as the kernel stack is not yet setup, which means we can't take a trap at this point. Signed-off-by:
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Naveen N. Rao authored
Introduce __head_end to mark end of the early fixed sections and use it to blacklist all exception handlers from kprobes. mpe: We do not need to do anything special for relocatable kernels, where the exception vectors are split from the main kernel, as the split vectors are already excluded by the check for kernel_text_address(). Signed-off-by:
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Naveen N. Rao authored
Along similar lines as commit 9326638c ("kprobes, x86: Use NOKPROBE_SYMBOL() instead of __kprobes annotation"), convert __kprobes annotation to either NOKPROBE_SYMBOL() or nokprobe_inline. The latter forces inlining, in which case the caller needs to be added to NOKPROBE_SYMBOL(). Also: - blacklist arch_deref_entry_point(), and - convert a few regular inlines to nokprobe_inline in lib/sstep.c A key benefit is the ability to detect such symbols as being blacklisted. Before this patch: $ cat /sys/kernel/debug/kprobes/blacklist | grep read_mem $ perf probe read_mem Failed to write event: Invalid argument Error: Failed to add events. $ dmesg | tail -1 [ 3736.112815] Could not insert probe at _text+10014968: -22 After patch: $ cat /sys/kernel/debug/kprobes/blacklist | grep read_mem 0xc000000000072b50-0xc000000000072d20 read_mem $ perf probe read_mem read_mem is blacklisted function, skip it. Added new events: (null):(null) (on read_mem) probe:read_mem (on read_mem) You can now use it in all perf tools, such as: perf record -e probe:read_mem -aR sleep 1 $ grep " read_mem" /proc/kallsyms c000000000072b50 t read_mem c0000000005f3b40 t read_mem $ cat /sys/kernel/debug/kprobes/list c0000000005f3b48 k read_mem+0x8 [DISABLED] Acked-by:
Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by:
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Naveen N. Rao authored
Move the stack setup and teardown code into ftrace_graph_caller(). This way, we don't incur the cost of setting it up unless function graph is enabled for this function. Also, remove the extraneous LR restore code after the function graph stub. LR has previously been restored and neither livepatch_handler() nor ftrace_graph_caller() return back here. Signed-off-by:
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Naveen N. Rao authored
set_current_kprobe() already saves regs->msr into kprobe_saved_msr. Remove the redundant save. Signed-off-by:
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Nicholas Piggin authored
The idle workaround does not need to load PACATOC, and it does not need to be called within a nested function that requires LR to be saved. Load the PACATOC at entry to the idle wakeup. It does not matter which PACA this comes from, so it's okay to call before the workaround. Then apply the workaround to get the right PACA. Signed-off-by:
Nicholas Piggin <npiggin@gmail.com> Signed-off-by:
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Nicholas Piggin authored
If not all threads were in winkle, full state loss recovery is not necessary and can be avoided. A previous patch removed this optimisation due to some complexity with the implementation. Re-implement it by counting the number of threads in winkle with the per-core idle state. Only restore full state loss if all threads were in winkle. This has a small window of false positives right before threads execute winkle and just after they wake up, when the winkle count does not reflect the true number of threads in winkle. This is not a significant problem in comparison with even the minimum winkle duration. For correctness, a false positive is not a problem (only false negatives would be). Reviewed-by:
Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by:
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Nicholas Piggin authored
When taking the core idle state lock, grab it immediately like a regular lock, rather than adding more tests in there. Holding the lock keeps it stable, so there is no need to do it whole holding the reservation. Reviewed-by:
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Nicholas Piggin authored
In preparation for adding more bits to the core idle state word, move the lock bit up, and unlock by flipping the lock bit rather than masking off all but the thread bits. Add branch hints for atomic operations while we're here. Reviewed-by:
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Nicholas Piggin authored
The ISA specifies power save wakeup due to a machine check exception can cause a machine check interrupt (rather than the usual system reset interrupt). The machine check handler copes with this by doing low level machine check recovery without restoring full state from idle, then queues up a machine check event for logging, then directly executes the same idle instruction it woke from. This minimises the work done before recovery is performed. The problem is that it requires machine specific instructions and knowledge of the book3s idle code. Currently it only has code to handle POWER8 idle, so POWER9 crashes when trying to execute the P8 idle instructions which don't exist in ISAv3.0B. cpu 0x0: Vector: e40 (Emulation Assist) at [c0000000008f3810] pc: c000000000008380: machine_check_handle_early+0x130/0x2f0 lr: c00000000053a098: stop_loop+0x68/0xd0 sp: c0000000008f3a90 msr: 9000000000081001 current = 0xc0000000008a1080 paca = 0xc00000000ffd0000 softe: 0 irq_happened: 0x01 pid = 0, comm = swapper/0 Instead of going to sleep after recovery, do the usual idle wakeup and state restoration by calling into the normal idle wakeup path. This reuses the normal idle wakeup paths. Reviewed-by:Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com> Signed-off-by:
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Nicholas Piggin authored
This reduces the number of nops for POWER8. Reviewed-by:
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Nicholas Piggin authored
The POWER8 idle code has a neat trick of programming the power on engine to restore a low bit into HSPRG0, so idle wakeup code can test and see if it has been programmed this way and therefore lost all state. Restore time can be reduced if winkle has not been reached. However this messes with our r13 PACA pointer, and requires HSPRG0 to be written to. It also optimizes the slowest and most uncommon case at the expense of another SPR write in the common nap state wakeup. Remove this complexity and assume winkle sleeps always require a state restore. This speedup could be made entirely contained within the winkle idle code by counting per-core winkles and setting a thread bitmap when all have gone to winkle. Reviewed-by:
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Nicholas Piggin authored
No functional change. Reviewed-by:
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Nicholas Piggin authored
The system reset idle handler system_reset_idle_common is relocated, so relocation is not required to branch to kvm_start_guest. The superfluous relocation does not result in incorrect code, but it does not compile outside of exception-64s.S (with fixed section definitions). Signed-off-by:
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- 21 Apr, 2017 2 commits
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Michael Ellerman authored
Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two sysctls that allow a user to configure the number of bits of randomness used for ASLR. Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to construct at least the MIN value in Kconfig, vs in a header which would be more natural. Given that we just go ahead and do it all in Kconfig. At least according to the code (the documentation makes no mention of it), the value is defined as the number of bits of randomisation *of the page*, not the address. This makes some sense, with larger page sizes more of the low bits are forced to zero, which would reduce the randomisation if we didn't take the PAGE_SIZE into account. However it does mean the min/max values have to change depending on the PAGE_SIZE in order to actually limit the amount of address space consumed by the randomisation. The result of that is that we have to define the default values based on both 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we have 128TB address space support on Book3S, we also have to take that into account. Finally we can wire up the value in arch_mmap_rnd(). Signed-off-by:
Bhupesh Sharma <bhsharma@redhat.com> Tested-by:
Kees Cook <keescook@chromium.org> Reviewed-by:
Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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Oliver O'Halloran authored
The default implementation of ioremap_cache() is aliased to ioremap(). On powerpc ioremap() creates cache-inhibited mappings by default which is almost certainly not what you wanted. Signed-off-by:
Oliver O'Halloran <oohall@gmail.com> Signed-off-by:
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- 20 Apr, 2017 8 commits
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Naveen N. Rao authored
On kprobe handler re-entry, try to emulate the instruction rather than single stepping always. Acked-by:
Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com> Signed-off-by:
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Naveen N. Rao authored
Factor out code to emulate instruction into a try_to_emulate() helper function. This makes no functional changes. Acked-by:
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Naveen N. Rao authored
With ABIv2, we offset 8 bytes into a function to get at the local entry point. mpe: NB this function is currently not called, the change to generic code to call it is being merged via the tip tree. Acked-by:
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Naveen N. Rao authored
commit 239aeba7 ("perf powerpc: Fix kprobe and kretprobe handling with kallsyms on ppc64le") changed how we use the offset field in struct kprobe on ABIv2. perf now offsets from the global entry point if an offset is specified and otherwise chooses the local entry point. Fix the same in kernel for kprobe API users. We do this by extending kprobe_lookup_name() to accept an additional parameter to indicate the offset specified with the kprobe registration. If offset is 0, we return the local function entry and return the global entry point otherwise. With: # cd /sys/kernel/debug/tracing/ # echo "p _do_fork" >> kprobe_events # echo "p _do_fork+0x10" >> kprobe_events before this patch: # cat ../kprobes/list c0000000000d0748 k _do_fork+0x8 [DISABLED] c0000000000d0758 k _do_fork+0x18 [DISABLED] c0000000000412b0 k kretprobe_trampoline+0x0 [OPTIMIZED] and after: # cat ../kprobes/list c0000000000d04c8 k _do_fork+0x8 [DISABLED] c0000000000d04d0 k _do_fork+0x10 [DISABLED] c0000000000412b0 k kretprobe_trampoline+0x0 [OPTIMIZED] Acked-by:
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Naveen N. Rao authored
The macro is now pretty long and ugly on powerpc. In the light of further changes needed here, convert it to a __weak variant to be over-ridden with a nicer looking function. Suggested-by:
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Masami Hiramatsu authored
Skip preparing optprobe if the probe is ftrace-based, since anyway, it must not be optimized (or already optimized by ftrace). Tested-by:
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Nicholas Piggin authored
Hypervisor Virtualization and Directed Hypervisor Doorbell interrupt handlers use the macro EXC_VIRT_OOL_MASKABLE_HV for their relocation-on handlers, which calls MASKABLE_RELON_EXCEPTION_HV_OOL, which uses the *real mode* interrupt prolog. This means we needlessly rfid from virtual mode to virtual mode. For POWER8 it only affects doorbell IPIs. Context switch microbenchmark between threads with snooze disabled (which causes IPI) gets about 3% faster, about 370 cycles. Should be more important on POWER9 with global doorbells and HVI for host interrupts. Use the RELON variant instead to reduce overhead. Fixes: 1707dd16 ("powerpc: Save CFAR before branching in interrupt entry paths") Signed-off-by:
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Michael Ellerman authored
Dan Carpenter noticed that the code in __xive_native_disable_queue() has a for loop with an unconditional break in the middle, which doesn't make a lot of sense. What the code's supposed to do is loop as long as OPAL says it's busy, if we get any other return code, either success or failure, then we should break the loop. So add the missing check. Fixes: 243e2511 ("powerpc/xive: Native exploitation of the XIVE interrupt controller") Reported-by:
Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by:
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- 19 Apr, 2017 7 commits
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Nicholas Piggin authored
Power9 DD1 does not implement SAO. Although it's not widely used, its presence or absence is visible to user space via arch_validate_prot() so it's moderately important that we get the value right. Fixes: 7dccfbc3 ("powerpc/book3s: Add a cpu table entry for different POWER9 revs") Signed-off-by:
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Nicholas Piggin authored
Power9 does not implement the icswx instruction. This CPU feature is not visible to userspace and is only used in the CONFIG_PPC_ICSWX code, which is generally not enabled, and can only be triggered by other code using icswx, which should not happen on Power9 systems in the first place. So impact should be minimal. Fixes: c3ab300e ("powerpc: Add POWER9 cputable entry") Signed-off-by:
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Madhavan Srinivasan authored
Patch add "mem_access" event to sysfs. This as-is not a raw event supported by Power8 pmu. Instead, it is formed based on raw event encoding specificed in isa207-common.h. Primary PMU event used here is PM_MRK_INST_CMPL. This event tracks only the completed marked instructions. Random sampling mode (MMCRA[SM]) with Random Instruction Sampling (RIS) is enabled to mark type of instructions. With Random sampling in RLS mode with PM_MRK_INST_CMPL event, the LDST /DATA_SRC fields in SIER identifies the memory hierarchy level (eg: L1, L2 etc) statisfied a data-cache miss for a marked instruction. Signed-off-by:
Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Signed-off-by:
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Madhavan Srinivasan authored
Patch to export SIER bits to userspace via perf_mem_data_src and perf_sample_data struct. Signed-off-by:
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Madhavan Srinivasan authored
Patch to export SIER bits to userspace via perf_mem_data_src and perf_sample_data struct. Signed-off-by:
Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Signed-off-by:
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Madhavan Srinivasan authored
Threshold feature when used with MMCRA [Threshold Event Counter Event], MMCRA[Threshold Start event] and MMCRA[Threshold End event] will update MMCRA[Threashold Event Counter Exponent] and MMCRA[Threshold Event Counter Multiplier] with the corresponding threshold event count values. Patch to export MMCRA[TECX/TECM] to userspace in 'weight' field of struct perf_sample_data. Signed-off-by:
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Madhavan Srinivasan authored
The LDST field and DATA_SRC in SIER identifies the memory hierarchy level (eg: L1, L2 etc), from which a data-cache miss for a marked instruction was satisfied. Use the 'perf_mem_data_src' object to export this hierarchy level to user space. Signed-off-by:
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