kernel.git/arch/mips/kvm/mips.c, branch linux-4.6.y

MIPS: KVM: Fix modular KVM under QEMU

2016-07-27T15:42:13Z

commit 797179bc4fe06c89e47a9f36f886f68640b423f8 upstream. Copy __kvm_mips_vcpu_run() into unmapped memory, so that we can never get a TLB refill exception in it when KVM is built as a module. This was observed to happen with the host MIPS kernel running under QEMU, due to a not entirely transparent optimisation in the QEMU TLB handling where TLB entries replaced with TLBWR are copied to a separate part of the TLB array. Code in those pages continue to be executable, but those mappings persist only until the next ASID switch, even if they are marked global. An ASID switch happens in __kvm_mips_vcpu_run() at exception level after switching to the guest exception base. Subsequent TLB mapped kernel instructions just prior to switching to the guest trigger a TLB refill exception, which enters the guest exception handlers without updating EPC. This appears as a guest triggered TLB refill on a host kernel mapped (host KSeg2) address, which is not handled correctly as user (guest) mode accesses to kernel (host) segments always generate address error exceptions. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Ralf Baechle Cc: kvm@vger.kernel.org Cc: linux-mips@linux-mips.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-03-15T02:14:06Z

Pull scheduler updates from Ingo Molnar: "The main changes in this cycle are: - Make schedstats a runtime tunable (disabled by default) and optimize it via static keys. As most distributions enable CONFIG_SCHEDSTATS=y due to its instrumentation value, this is a nice performance enhancement. (Mel Gorman) - Implement 'simple waitqueues' (swait): these are just pure waitqueues without any of the more complex features of full-blown waitqueues (callbacks, wake flags, wake keys, etc.). Simple waitqueues have less memory overhead and are faster. Use simple waitqueues in the RCU code (in 4 different places) and for handling KVM vCPU wakeups. (Peter Zijlstra, Daniel Wagner, Thomas Gleixner, Paul Gortmaker, Marcelo Tosatti) - sched/numa enhancements (Rik van Riel) - NOHZ performance enhancements (Rik van Riel) - Various sched/deadline enhancements (Steven Rostedt) - Various fixes (Peter Zijlstra) - ... and a number of other fixes, cleanups and smaller enhancements" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (29 commits) sched/cputime: Fix steal_account_process_tick() to always return jiffies sched/deadline: Remove dl_new from struct sched_dl_entity Revert "kbuild: Add option to turn incompatible pointer check into error" sched/deadline: Remove superfluous call to switched_to_dl() sched/debug: Fix preempt_disable_ip recording for preempt_disable() sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity time, acct: Drop irq save & restore from __acct_update_integrals() acct, time: Change indentation in __acct_update_integrals() sched, time: Remove non-power-of-two divides from __acct_update_integrals() sched/rt: Kick RT bandwidth timer immediately on start up sched/debug: Add deadline scheduler bandwidth ratio to /proc/sched_debug sched/debug: Move sched_domain_sysctl to debug.c sched/debug: Move the /sys/kernel/debug/sched_features file setup into debug.c sched/rt: Fix PI handling vs. sched_setscheduler() sched/core: Remove duplicated sched_group_set_shares() prototype sched/fair: Consolidate nohz CPU load update code sched/fair: Avoid using decay_load_missed() with a negative value sched/deadline: Always calculate end of period on sched_yield() sched/cgroup: Fix cgroup entity load tracking tear-down rcu: Use simple wait queues where possible in rcutree ...

mips/kvm: fix ioctl error handling

2016-03-02T09:34:52Z

Returning directly whatever copy_to_user(...) or copy_from_user(...) returns may not do the right thing if there's a pagefault: copy_to_user/copy_from_user return the number of bytes not copied in this case, but ioctls need to return -EFAULT instead. Fix up kvm on mips to do return copy_to_user(...)) ? -EFAULT : 0; and return copy_from_user(...)) ? -EFAULT : 0; everywhere. Cc: stable@vger.kernel.org Signed-off-by: Michael S. Tsirkin Signed-off-by: Paolo Bonzini

KVM: Use simple waitqueue for vcpu->wq

2016-02-25T10:27:16Z

The problem: On -rt, an emulated LAPIC timer instances has the following path: 1) hard interrupt 2) ksoftirqd is scheduled 3) ksoftirqd wakes up vcpu thread 4) vcpu thread is scheduled This extra context switch introduces unnecessary latency in the LAPIC path for a KVM guest. The solution: Allow waking up vcpu thread from hardirq context, thus avoiding the need for ksoftirqd to be scheduled. Normal waitqueues make use of spinlocks, which on -RT are sleepable locks. Therefore, waking up a waitqueue waiter involves locking a sleeping lock, which is not allowed from hard interrupt context. cyclictest command line: This patch reduces the average latency in my tests from 14us to 11us. Daniel writes: Paolo asked for numbers from kvm-unit-tests/tscdeadline_latency benchmark on mainline. The test was run 1000 times on tip/sched/core 4.4.0-rc8-01134-g0905f04: ./x86-run x86/tscdeadline_latency.flat -cpu host with idle=poll. The test seems not to deliver really stable numbers though most of them are smaller. Paolo write: "Anything above ~10000 cycles means that the host went to C1 or lower---the number means more or less nothing in that case. The mean shows an improvement indeed." Before: min max mean std count 1000.000000 1000.000000 1000.000000 1000.000000 mean 5162.596000 2019270.084000 5824.491541 20681.645558 std 75.431231 622607.723969 89.575700 6492.272062 min 4466.000000 23928.000000 5537.926500 585.864966 25% 5163.000000 1613252.750000 5790.132275 16683.745433 50% 5175.000000 2281919.000000 5834.654000 23151.990026 75% 5190.000000 2382865.750000 5861.412950 24148.206168 max 5228.000000 4175158.000000 6254.827300 46481.048691 After min max mean std count 1000.000000 1000.00000 1000.000000 1000.000000 mean 5143.511000 2076886.10300 5813.312474 21207.357565 std 77.668322 610413.09583 86.541500 6331.915127 min 4427.000000 25103.00000 5529.756600 559.187707 25% 5148.000000 1691272.75000 5784.889825 17473.518244 50% 5160.000000 2308328.50000 5832.025000 23464.837068 75% 5172.000000 2393037.75000 5853.177675 24223.969976 max 5222.000000 3922458.00000 6186.720500 42520.379830 [Patch was originaly based on the swait implementation found in the -rt tree. Daniel ported it to mainline's version and gathered the benchmark numbers for tscdeadline_latency test.] Signed-off-by: Daniel Wagner Acked-by: Peter Zijlstra (Intel) Cc: linux-rt-users@vger.kernel.org Cc: Boqun Feng Cc: Marcelo Tosatti Cc: Steven Rostedt Cc: Paul Gortmaker Cc: Paolo Bonzini Cc: "Paul E. McKenney" Link: http://lkml.kernel.org/r/1455871601-27484-4-git-send-email-wagi@monom.org Signed-off-by: Thomas Gleixner

MIPS: KVM: Add missing newline to kvm_err()

2016-01-24T02:38:48Z

Add missing newline to end of kvm_err string when guest PMAP couldn't be allocated. Signed-off-by: James Hogan Cc: Gleb Natapov Cc: Paolo Bonzini Cc: kvm@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/11896/ Signed-off-by: Ralf Baechle

MIPS: Move Cause.ExcCode trap codes to mipsregs.h

2016-01-24T02:15:51Z

Move the Cause.ExcCode trap code definitions from kvm_host.h to mipsregs.h, since they describe architectural bits rather than KVM specific constants, and change the prefix from T_ to EXCCODE_. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: Gleb Natapov Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/11891/ Signed-off-by: Ralf Baechle

MIPS: KVM: Make kvm_mips_{init,exit}() static

2016-01-24T02:15:01Z

The module init and exit functions have no need to be global, so make them static. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: Gleb Natapov Cc: kvm@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/11889/ Signed-off-by: Ralf Baechle

MIPS: KVM: Uninit VCPU in vcpu_create error path

2015-11-18T11:25:36Z

If either of the memory allocations in kvm_arch_vcpu_create() fail, the vcpu which has been allocated and kvm_vcpu_init'd doesn't get uninit'd in the error handling path. Add a call to kvm_vcpu_uninit() to fix this. Fixes: 669e846e6c4e ("KVM/MIPS32: MIPS arch specific APIs for KVM") Signed-off-by: James Hogan Cc: Ralf Baechle Cc: Paolo Bonzini Cc: Gleb Natapov Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Cc: # 3.10.x- Signed-off-by: Paolo Bonzini

KVM: add halt_attempted_poll to VCPU stats

2015-09-16T10:17:00Z

This new statistic can help diagnosing VCPUs that, for any reason, trigger bad behavior of halt_poll_ns autotuning. For example, say halt_poll_ns = 480000, and wakeups are spaced exactly like 479us, 481us, 479us, 481us. Then KVM always fails polling and wastes 10+20+40+80+160+320+480 = 1110 microseconds out of every 479+481+479+481+479+481+479 = 3359 microseconds. The VCPU then is consuming about 30% more CPU than it would use without polling. This would show as an abnormally high number of attempted polling compared to the successful polls. Acked-by: Christian Borntraeger Signed-off-by: Paolo Bonzini

KVM: add "new" argument to kvm_arch_commit_memory_region

2015-05-28T08:42:58Z

This lets the function access the new memory slot without going through kvm_memslots and id_to_memslot. It will simplify the code when more than one address space will be supported. Unfortunately, the "const"ness of the new argument must be casted away in two places. Fixing KVM to accept const struct kvm_memory_slot pointers would require modifications in pretty much all architectures, and is left for later. Reviewed-by: Radim Krcmar Signed-off-by: Paolo Bonzini