- 12 May, 2021 35 commits
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Alexey Dobriyan authored
Creating 2**32 tasks to wait in D-state is impossible and wasteful. Return "unsigned int" and save on REX prefixes. Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:
Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210422200228.1423391-2-adobriyan@gmail.com
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Alexey Dobriyan authored
Creating 2**32 tasks is impossible due to futex pid limits and wasteful anyway. Nobody has done it. Bring nr_running() into 32-bit world to save on REX prefixes. Signed-off-by:
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Ingo Molnar authored
A few more snuck in. Also capitalize 'CPU' while at it. Signed-off-by: -
Valentin Schneider authored
As pointed out by commit de9b8f5d ("sched: Fix crash trying to dequeue/enqueue the idle thread") init_idle() can and will be invoked more than once on the same idle task. At boot time, it is invoked for the boot CPU thread by sched_init(). Then smp_init() creates the threads for all the secondary CPUs and invokes init_idle() on them. As the hotplug machinery brings the secondaries to life, it will issue calls to idle_thread_get(), which itself invokes init_idle() yet again. In this case it's invoked twice more per secondary: at _cpu_up(), and at bringup_cpu(). Given smp_init() already initializes the idle tasks for all *possible* CPUs, no further initialization should be required. Now, removing init_idle() from idle_thread_get() exposes some interesting expectations with regards to the idle task's preempt_count: the secondary startup always issues a preempt_disable(), requiring some reset of the preempt count to 0 between hot-unplug and hotplug, which is currently served by idle_thread_get() -> idle_init(). Given the idle task is supposed to have preemption disabled once and never see it re-enabled, it seems that what we actually want is to initialize its preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove init_idle() from idle_thread_get(). Secondary startups were patched via coccinelle: @begone@ @@ -preempt_disable(); ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); Signed-off-by:
Valentin Schneider <valentin.schneider@arm.com> Signed-off-by:
Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
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Chris Hyser authored
Provides a selftest and examples of using the interface. [peterz: updated to not use sched_debug] Signed-off-by:
Chris Hyser <chris.hyser@oracle.com> Signed-off-by:
Don Hiatt <dhiatt@digitalocean.com> Tested-by:
Hongyu Ning <hongyu.ning@linux.intel.com> Tested-by:
Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/20210422123309.100860030@infradead.org
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Chris Hyser authored
This patch provides support for setting and copying core scheduling 'task cookies' between threads (PID), processes (TGID), and process groups (PGID). The value of core scheduling isn't that tasks don't share a core, 'nosmt' can do that. The value lies in exploiting all the sharing opportunities that exist to recover possible lost performance and that requires a degree of flexibility in the API. From a security perspective (and there are others), the thread, process and process group distinction is an existent hierarchal categorization of tasks that reflects many of the security concerns about 'data sharing'. For example, protecting against cache-snooping by a thread that can just read the memory directly isn't all that useful. With this in mind, subcommands to CREATE/SHARE (TO/FROM) provide a mechanism to create and share cookies. CREATE/SHARE_TO specify a target pid with enum pidtype used to specify the scope of the targeted tasks. For example, PIDTYPE_TGID will share the cookie with the process and all of it's threads as typically desired in a security scenario. API: prctl(PR_SCHED_CORE, PR_SCHED_CORE_GET, tgtpid, pidtype, &cookie) prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, tgtpid, pidtype, NULL) prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_TO, tgtpid, pidtype, NULL) prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_FROM, srcpid, pidtype, NULL) where 'tgtpid/srcpid == 0' implies the current process and pidtype is kernel enum pid_type {PIDTYPE_PID, PIDTYPE_TGID, PIDTYPE_PGID, ...}. For return values, EINVAL, ENOMEM are what they say. ESRCH means the tgtpid/srcpid was not found. EPERM indicates lack of PTRACE permission access to tgtpid/srcpid. ENODEV indicates your machines lacks SMT. [peterz: complete rewrite] Signed-off-by: -
Peter Zijlstra authored
Note that sched_core_fork() is called from under tasklist_lock, and not from sched_fork() earlier. This avoids a few races later. Signed-off-by:
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Peter Zijlstra authored
In order to not have to use pid_struct, create a new, smaller, structure to manage task cookies for core scheduling. Signed-off-by:
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Aubrey Li authored
- Don't migrate if there is a cookie mismatch Load balance tries to move task from busiest CPU to the destination CPU. When core scheduling is enabled, if the task's cookie does not match with the destination CPU's core cookie, this task may be skipped by this CPU. This mitigates the forced idle time on the destination CPU. - Select cookie matched idle CPU In the fast path of task wakeup, select the first cookie matched idle CPU instead of the first idle CPU. - Find cookie matched idlest CPU In the slow path of task wakeup, find the idlest CPU whose core cookie matches with task's cookie Signed-off-by:Aubrey Li <aubrey.li@linux.intel.com> Signed-off-by:
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Peter Zijlstra authored
When a sibling is forced-idle to match the core-cookie; search for matching tasks to fill the core. rcu_read_unlock() can incur an infrequent deadlock in sched_core_balance(). Fix this by using the RCU-sched flavor instead. Signed-off-by:
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Joel Fernandes (Google) authored
During force-idle, we end up doing cross-cpu comparison of vruntimes during pick_next_task. If we simply compare (vruntime-min_vruntime) across CPUs, and if the CPUs only have 1 task each, we will always end up comparing 0 with 0 and pick just one of the tasks all the time. This starves the task that was not picked. To fix this, take a snapshot of the min_vruntime when entering force idle and use it for comparison. This min_vruntime snapshot will only be used for cross-CPU vruntime comparison, and nothing else. A note about the min_vruntime snapshot and force idling: During selection: When we're not fi, we need to update snapshot. when we're fi and we were not fi, we must update snapshot. When we're fi and we were already fi, we must not update snapshot. Which gives: fib fi update 0 0 1 0 1 1 1 0 1 1 1 0 Where: fi: force-idled now fib: force-idled before So the min_vruntime snapshot needs to be updated when: !(fib && fi). Also, the cfs_prio_less() function needs to be aware of whether the core is in force idle or not, since it will be use this information to know whether to advance a cfs_rq's min_vruntime_fi in the hierarchy. So pass this information along via pick_task() -> prio_less(). Suggested-by:
Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by:
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Joel Fernandes (Google) authored
The rationale is as follows. In the core-wide pick logic, even if need_sync == false, we need to go look at other CPUs (non-local CPUs) to see if they could be running RT. Say the RQs in a particular core look like this: Let CFS1 and CFS2 be 2 tagged CFS tags. Let RT1 be an untagged RT task. rq0 rq1 CFS1 (tagged) RT1 (no tag) CFS2 (tagged) Say schedule() runs on rq0. Now, it will enter the above loop and pick_task(RT) will return NULL for 'p'. It will enter the above if() block and see that need_sync == false and will skip RT entirely. The end result of the selection will be (say prio(CFS1) > prio(CFS2)): rq0 rq1 CFS1 IDLE When it should have selected: rq0 rq1 IDLE RT Suggested-by:
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Vineeth Pillai authored
If there is only one long running local task and the sibling is forced idle, it might not get a chance to run until a schedule event happens on any cpu in the core. So we check for this condition during a tick to see if a sibling is starved and then give it a chance to schedule. Signed-off-by:
Vineeth Pillai <viremana@linux.microsoft.com> Signed-off-by:
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Peter Zijlstra authored
Instead of only selecting a local task, select a task for all SMT siblings for every reschedule on the core (irrespective which logical CPU does the reschedule). Signed-off-by:
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Peter Zijlstra authored
Introduce task_struct::core_cookie as an opaque identifier for core scheduling. When enabled; core scheduling will only allow matching task to be on the core; where idle matches everything. When task_struct::core_cookie is set (and core scheduling is enabled) these tasks are indexed in a second RB-tree, first on cookie value then on scheduling function, such that matching task selection always finds the most elegible match. NOTE: *shudder* at the overhead... NOTE: *sigh*, a 3rd copy of the scheduling function; the alternative is per class tracking of cookies and that just duplicates a lot of stuff for no raisin (the 2nd copy lives in the rt-mutex PI code). [Joel: folded fixes] Signed-off-by:
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Peter Zijlstra authored
Because sched_class::pick_next_task() also implies sched_class::set_next_task() (and possibly put_prev_task() and newidle_balance) it is not state invariant. This makes it unsuitable for remote task selection. Signed-off-by:
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Peter Zijlstra authored
Stuff the meat of sched_core_put() into a work such that we can use sched_core_put() from atomic context. Signed-off-by:
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Peter Zijlstra authored
rq_lockp() includes a static_branch(), which is asm-goto, which is asm volatile which defeats regular CSE. This means that: if (!static_branch(&foo)) return simple; if (static_branch(&foo) && cond) return complex; Doesn't fold and we get horrible code. Introduce __rq_lockp() without the static_branch() on. Signed-off-by:
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Peter Zijlstra authored
Introduce the basic infrastructure to have a core wide rq->lock. This relies on the rq->__lock order being in increasing CPU number (inside a core). It is also constrained to SMT8 per lockdep (and SMT256 per preempt_count). Luckily SMT8 is the max supported SMT count for Linux (Mips, Sparc and Power are known to have this). Signed-off-by:
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Peter Zijlstra authored
When switching on core-sched, CPUs need to agree which lock to use for their RQ. The new rule will be that rq->core_enabled will be toggled while holding all rq->__locks that belong to a core. This means we need to double check the rq->core_enabled value after each lock acquire and retry if it changed. This also has implications for those sites that take multiple RQ locks, they need to be careful that the second lock doesn't end up being the first lock. Verify the lock pointer after acquiring the first lock, because if they're on the same core, holding any of the rq->__lock instances will pin the core state. While there, change the rq->__lock order to CPU number, instead of rq address, this greatly simplifies the next patch. Signed-off-by:
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Peter Zijlstra authored
In preparation of playing games with rq->lock, abstract the thing using an accessor. Signed-off-by:
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Peter Zijlstra authored
In prepration for playing games with rq->lock, add some rq_lock wrappers. Signed-off-by:
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Peter Zijlstra authored
Signed-off-by:
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Peter Zijlstra authored
Just like sched_schedstats, allow runtime enabling (and disabling) of delayacct. This is useful if one forgot to add the delayacct boot time option. Signed-off-by:
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Peter Zijlstra authored
Assuming this stuff isn't actually used much; disable it by default and avoid allocating and tracking the task_delay_info structure. taskstats is changed to still report the regular sched and sched_info and only skip the missing task_delay_info fields instead of not reporting anything. Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Reviewed-by:
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Peter Zijlstra authored
Cheaper when delayacct is disabled. Signed-off-by:
Balbir Singh <bsingharora@gmail.com> Acked-by:
Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/20210505111525.248028369@infradead.org
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Peter Zijlstra authored
AFAICT KVM only relies on SCHED_INFO. Nothing uses the p->delays data that belongs to TASK_DELAY_ACCT. Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com> Acked-by:
Marc Zyngier <maz@kernel.org> Acked-by:
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Peter Zijlstra authored
The situation around sched_info is somewhat complicated, it is used by sched_stats and delayacct and, indirectly, kvm. If SCHEDSTATS=Y (but disabled by default) sched_info_on() is unconditionally true -- this is the case for all distro kernel configs I checked. If for some reason SCHEDSTATS=N, but TASK_DELAY_ACCT=Y, then sched_info_on() can return false when delayacct is disabled, presumably because there would be no other users left; except kvm is. Instead of complicating matters further by accurately accounting sched_stat and kvm state, simply unconditionally enable when SCHED_INFO=Y, matching the common distro case. Signed-off-by:
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Peter Zijlstra authored
For consistency, rename {queued,dequeued} to {enqueue,dequeue}. Signed-off-by:Rik van Riel <riel@surriel.com> Reviewed-by:
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Peter Zijlstra authored
Like all scheduler statistics, use sched_clock() based time. Signed-off-by:
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Pierre Gondois authored
find_energy_efficient_cpu() (feec()) searches the best energy CPU to place a task on. To do so, compute_energy() estimates the energy impact of placing the task on a CPU, based on CPU and task utilization signals. Utilization signals can be concurrently updated while evaluating a performance domain (pd). In some cases, this leads to having a 'negative delta', i.e. placing the task in the pd is seen as an energy gain. Thus, any further energy comparison is biased. In case of a 'negative delta', return prev_cpu since: 1. a 'negative delta' happens in less than 0.5% of feec() calls, on a Juno with 6 CPUs (4 little, 2 big) 2. it is unlikely to have two consecutive 'negative delta' for a task, so if the first call fails, feec() will correctly place the task in the next feec() call 3. EAS current behavior tends to select prev_cpu if the task doesn't raise the OPP of its current pd. prev_cpu is EAS's generic decision 4. prev_cpu should be preferred to returning an error code. In the latter case, select_idle_sibling() would do the placement, selecting a big (and not energy efficient) CPU. As 3., the task would potentially reside on the big CPU for a long time Reported-by:
Xuewen Yan <xuewen.yan@unisoc.com> Suggested-by:
Pierre Gondois <Pierre.Gondois@arm.com> Signed-off-by:
Lukasz Luba <lukasz.luba@arm.com> Reviewed-by:
Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by:
Vincent Donnefort <vincent.donnefort@arm.com> Link: https://lkml.kernel.org/r/20210504090743.9688-3-Pierre.Gondois@arm.com
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Pierre Gondois authored
find_energy_efficient_cpu() searches the best energy CPU to place a task on. To do so, the energy of each performance domain (pd) is computed w/ and w/o the task placed on it. The energy of a pd w/o the task (base_energy_pd) is computed prior knowing whether a CPU is available in the pd. Move the base_energy_pd computation after looping through the CPUs of a pd and only compute it if at least one CPU is available. Suggested-by:
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Rik van Riel authored
The try_to_wake_up function has an optimization where it can queue a task for wakeup on its previous CPU, if the task is still in the middle of going to sleep inside schedule(). Once schedule() re-enables IRQs, the task will be woken up with an IPI, and placed back on the runqueue. If we have such a wakeup pending, there is no need to search other CPUs for runnable tasks. Just skip (or bail out early from) newidle balancing, and run the just woken up task. For a memcache like workload test, this reduces total CPU use by about 2%, proportionally split between user and system time, and p99 and p95 application response time by 10% on average. The schedstats run_delay number shows a similar improvement. Signed-off-by:
Mel Gorman <mgorman@suse.de> Link: https://lkml.kernel.org/r/20210422130236.0bb353df@imladris.surriel.com
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Oleg Nesterov authored
container_of() can never return NULL - so don't check for it pointlessly. [ mingo: Twiddled the changelog. ] Signed-off-by:
Oleg Nesterov <oleg@redhat.com> Signed-off-by:
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Gautham R. Shenoy authored
In commit: 9fe1f127 ("sched/fair: Merge select_idle_core/cpu()") in select_idle_cpu(), we check if an idle core is present in the LLC of the target CPU via the flag "has_idle_cores". We look for the idle core in select_idle_cores(). If select_idle_cores() isn't able to find an idle core/CPU, we need to unset the has_idle_cores flag in the LLC of the target to prevent other CPUs from going down this route. However, the current code is unsetting it in the LLC of the current CPU instead of the target CPU. This patch fixes this issue. Fixes: 9fe1f127 ("sched/fair: Merge select_idle_core/cpu()") Signed-off-by:
Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by:
Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by:
Mel Gorman <mgorman@techsingularity.net> Link: https://lore.kernel.org/r/1620746169-13996-1-git-send-email-ego@linux.vnet.ibm.com
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- 11 May, 2021 2 commits
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linuxLinus Torvalds authored
Pull btrfs fix from David Sterba: "Handle transaction start error in btrfs_fileattr_set() This is fix for code introduced by the new fileattr merge" * tag 'for-5.13-rc1-part2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: handle transaction start error in btrfs_fileattr_set
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Ritesh Harjani authored
Add error handling in btrfs_fileattr_set in case of an error while starting a transaction. This fixes btrfs/232 which otherwise used to fail with below signature on Power. btrfs/232 [ 1119.474650] run fstests btrfs/232 at 2021-04-21 02:21:22 <...> [ 1366.638585] BUG: Unable to handle kernel data access on read at 0xffffffffffffff86 [ 1366.638768] Faulting instruction address: 0xc0000000009a5c88 cpu 0x0: Vector: 380 (Data SLB Access) at [c000000014f177b0] pc: c0000000009a5c88: btrfs_update_root_times+0x58/0xc0 lr: c0000000009a5c84: btrfs_update_root_times+0x54/0xc0 <...> pid = 24881, comm = fsstress btrfs_update_inode+0xa0/0x140 btrfs_fileattr_set+0x5d0/0x6f0 vfs_fileattr_set+0x2a8/0x390 do_vfs_ioctl+0x1290/0x1ac0 sys_ioctl+0x6c/0x120 system_call_exception+0x3d4/0x410 system_call_common+0xec/0x278 Fixes: 97fc2977 ("btrfs: convert to fileattr") Signed-off-by:Ritesh Harjani <riteshh@linux.ibm.com> Reviewed-by:
David Sterba <dsterba@suse.com> Signed-off-by:
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- 10 May, 2021 3 commits
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Linus Torvalds authored
Merge tag 'perf-tools-fixes-for-v5.13-2021-05-10' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux Pull perf tools fixes from Arnaldo Carvalho de Melo: - Fix swapping of cpu_map and stat_config records. - Fix dynamic libbpf linking. - Disallow -c and -F option at the same time in 'perf record'. - Update headers with the kernel originals. - Silence warning for JSON ArchStd files. - Fix a build error on arm64 with clang. * tag 'perf-tools-fixes-for-v5.13-2021-05-10' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: tools headers UAPI: Sync perf_event.h with the kernel sources tools headers cpufeatures: Sync with the kernel sources tools include UAPI powerpc: Sync errno.h with the kernel headers tools arch: Update arch/x86/lib/mem{cpy,set}_64.S copies used in 'perf bench mem memcpy' tools headers UAPI: Sync linux/prctl.h with the kernel sources tools headers UAPI: Sync files changed by landlock, quotactl_path and mount_settattr new syscalls perf tools: Fix a build error on arm64 with clang tools headers kvm: Sync kvm headers with the kernel sources tools headers UAPI: Sync linux/kvm.h with the kernel sources perf tools: Fix dynamic libbpf link perf session: Fix swapping of cpu_map and stat_config records perf jevents: Silence warning for ArchStd files perf record: Disallow -c and -F option at the same time tools arch x86: Sync the msr-index.h copy with the kernel sources tools headers UAPI: Sync drm/i915_drm.h with the kernel sources tools headers UAPI: Update tools's copy of drm.h headers
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linuxLinus Torvalds authored
Pull btrfs fixes from David Sterba: "First batch of various fixes, here's a list of notable ones: - fix unmountable seed device after fstrim - fix silent data loss in zoned mode due to ordered extent splitting - fix race leading to unpersisted data and metadata on fsync - fix deadlock when cloning inline extents and using qgroups" * tag 'for-5.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: initialize return variable in cleanup_free_space_cache_v1 btrfs: zoned: sanity check zone type btrfs: fix unmountable seed device after fstrim btrfs: fix deadlock when cloning inline extents and using qgroups btrfs: fix race leading to unpersisted data and metadata on fsync btrfs: do not consider send context as valid when trying to flush qgroups btrfs: zoned: fix silent data loss after failure splitting ordered extent
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git://git.kernel.org/pub/scm/virt/kvm/kvmLinus Torvalds authored
Pull kvm fixes from Paolo Bonzini: - Lots of bug fixes. - Fix virtualization of RDPID - Virtualization of DR6_BUS_LOCK, which on bare metal is new to this release - More nested virtualization migration fixes (nSVM and eVMCS) - Fix for KVM guest hibernation - Fix for warning in SEV-ES SRCU usage - Block KVM from loading on AMD machines with 5-level page tables, due to the APM not mentioning how host CR4.LA57 exactly impacts the guest. * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (48 commits) KVM: SVM: Move GHCB unmapping to fix RCU warning KVM: SVM: Invert user pointer casting in SEV {en,de}crypt helpers kvm: Cap halt polling at kvm->max_halt_poll_ns tools/kvm_stat: Fix documentation typo KVM: x86: Prevent deadlock against tk_core.seq KVM: x86: Cancel pvclock_gtod_work on module removal KVM: x86: Prevent KVM SVM from loading on kernels with 5-level paging KVM: X86: Expose bus lock debug exception to guest KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit KVM: PPC: Book3S HV: Fix conversion to gfn-based MMU notifier callbacks KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model KVM: x86: Move uret MSR slot management to common x86 KVM: x86: Export the number of uret MSRs to vendor modules KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way KVM: VMX: Use common x86's uret MSR list as the one true list KVM: VMX: Use flag to indicate "active" uret MSRs instead of sorting list KVM: VMX: Configure list of user return MSRs at module init KVM: x86: Add support for RDPID without RDTSCP KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host ...
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