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  1. 09 1月, 2017 4 次提交
  3. 26 12月, 2016 1 次提交
    • T
      ktime: Cleanup ktime_set() usage · 8b0e1953
      由 Thomas Gleixner 提交于 
      ktime_set(S,N) was required for the timespec storage type and is still
useful for situations where a Seconds and Nanoseconds part of a time value
needs to be converted. For anything where the Seconds argument is 0, this
is pointless and can be replaced with a simple assignment.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
      8b0e1953
  5. 25 11月, 2016 1 次提交
    • R
      KVM: x86: fix out-of-bounds access in lapic · 444fdad8
      由 Radim Krčmář 提交于 
      Cluster xAPIC delivery incorrectly assumed that dest_id <= 0xff.
With enabled KVM_X2APIC_API_USE_32BIT_IDS in KVM_CAP_X2APIC_API, a
userspace can send an interrupt with dest_id that results in
out-of-bounds access.

Found by syzkaller:

  BUG: KASAN: slab-out-of-bounds in kvm_irq_delivery_to_apic_fast+0x11fa/0x1210 at addr ffff88003d9ca750
  Read of size 8 by task syz-executor/22923
  CPU: 0 PID: 22923 Comm: syz-executor Not tainted 4.9.0-rc4+ #49
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
   [...]
  Call Trace:
   [...] __dump_stack lib/dump_stack.c:15
   [...] dump_stack+0xb3/0x118 lib/dump_stack.c:51
   [...] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156
   [...] print_address_description mm/kasan/report.c:194
   [...] kasan_report_error mm/kasan/report.c:283
   [...] kasan_report+0x231/0x500 mm/kasan/report.c:303
   [...] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:329
   [...] kvm_irq_delivery_to_apic_fast+0x11fa/0x1210 arch/x86/kvm/lapic.c:824
   [...] kvm_irq_delivery_to_apic+0x132/0x9a0 arch/x86/kvm/irq_comm.c:72
   [...] kvm_set_msi+0x111/0x160 arch/x86/kvm/irq_comm.c:157
   [...] kvm_send_userspace_msi+0x201/0x280 arch/x86/kvm/../../../virt/kvm/irqchip.c:74
   [...] kvm_vm_ioctl+0xba5/0x1670 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3015
   [...] vfs_ioctl fs/ioctl.c:43
   [...] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679
   [...] SYSC_ioctl fs/ioctl.c:694
   [...] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
   [...] entry_SYSCALL_64_fastpath+0x1f/0xc2
Reported-by: NDmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Fixes: e45115b6 ("KVM: x86: use physical LAPIC array for logical x2APIC")
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      444fdad8
  7. 22 11月, 2016 1 次提交
  9. 03 11月, 2016 7 次提交
  11. 19 8月, 2016 1 次提交
  13. 04 8月, 2016 1 次提交
    • W
      KVM: lapic: fix access preemption timer stuff even if kernel_irqchip=off · 91005300
      由 Wanpeng Li 提交于 
      BUG: unable to handle kernel NULL pointer dereference at 000000000000008c
IP: [<ffffffffc04e0180>] kvm_lapic_hv_timer_in_use+0x10/0x20 [kvm]
PGD 0
Oops: 0000 [#1] SMP
Call Trace:
 kvm_arch_vcpu_load+0x86/0x260 [kvm]
 vcpu_load+0x46/0x60 [kvm]
 kvm_vcpu_ioctl+0x79/0x7c0 [kvm]
 ? __lock_is_held+0x54/0x70
 do_vfs_ioctl+0x96/0x6a0
 ? __fget_light+0x2a/0x90
 SyS_ioctl+0x79/0x90
 do_syscall_64+0x7c/0x1e0
 entry_SYSCALL64_slow_path+0x25/0x25
RIP  [<ffffffffc04e0180>] kvm_lapic_hv_timer_in_use+0x10/0x20 [kvm]
 RSP <ffff8800db1f3d70>
CR2: 000000000000008c
---[ end trace a55fb79d2b3b4ee8 ]---

This can be reproduced steadily by kernel_irqchip=off.

We should not access preemption timer stuff if lapic is emulated in userspace.
This patch fix it by avoiding access preemption timer stuff when kernel_irqchip=off.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      91005300
  15. 14 7月, 2016 10 次提交
  17. 01 7月, 2016 2 次提交
    • W
      KVM: vmx: fix missed cancellation of TSC deadline timer · 196f20ca
      由 Wanpeng Li 提交于 
      INFO: rcu_sched detected stalls on CPUs/tasks:
 1-...: (11800 GPs behind) idle=45d/140000000000000/0 softirq=0/0 fqs=21663
 (detected by 0, t=65016 jiffies, g=11500, c=11499, q=719)
Task dump for CPU 1:
qemu-system-x86 R  running task        0  3529   3525 0x00080808
 ffff8802021791a0 ffff880212895040 0000000000000001 00007f1c2c00db40
 ffff8801dd20fcd3 ffffc90002b98000 ffff8801dd20fc88 ffff8801dd20fcf8
 0000000000000286 ffff8801dd2ac538 ffff8801dd20fcc0 ffffffffc06949c9
Call Trace:
? kvm_write_guest_cached+0xb9/0x160 [kvm]
? __delay+0xf/0x20
? wait_lapic_expire+0x14a/0x200 [kvm]
? kvm_arch_vcpu_ioctl_run+0xcbe/0x1b00 [kvm]
? kvm_arch_vcpu_ioctl_run+0xe34/0x1b00 [kvm]
? kvm_vcpu_ioctl+0x2d3/0x7c0 [kvm]
? __fget+0x5/0x210
? do_vfs_ioctl+0x96/0x6a0
? __fget_light+0x2a/0x90
? SyS_ioctl+0x79/0x90
? do_syscall_64+0x7c/0x1e0
? entry_SYSCALL64_slow_path+0x25/0x25

This can be reproduced readily by running a full dynticks guest(since hrtimer
in guest is heavily used) w/ lapic_timer_advance disabled.

If fail to program hardware preemption timer, we will fallback to hrtimer based
method, however, a previous programmed preemption timer miss to cancel in this
scenario which results in one hardware preemption timer and one hrtimer emulated
tsc deadline timer run simultaneously. So sometimes the target guest deadline
tsc is earlier than guest tsc, which leads to the computation in vmx_set_hv_timer
can underflow and cause delta_tsc to be set a huge value, then host soft lockup
as above.

This patch fix it by cancelling the previous programmed preemption timer if there
is once we failed to program the new preemption timer and fallback to hrtimer
based method.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      196f20ca
    • W
      KVM: x86: introduce cancel_hv_tscdeadline · bd97ad0e
      由 Wanpeng Li 提交于 
      Introduce cancel_hv_tscdeadline() to encapsulate preemption
timer cancel stuff.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      bd97ad0e
  19. 27 6月, 2016 1 次提交
  21. 16 6月, 2016 2 次提交
    • Y
      KVM: x86: support using the vmx preemption timer for tsc deadline timer · ce7a058a
      由 Yunhong Jiang 提交于 
      The VMX preemption timer can be used to virtualize the TSC deadline timer.
The VMX preemption timer is armed when the vCPU is running, and a VMExit
will happen if the virtual TSC deadline timer expires.

When the vCPU thread is blocked because of HLT, KVM will switch to use
an hrtimer, and then go back to the VMX preemption timer when the vCPU
thread is unblocked.

This solution avoids the complex OS's hrtimer system, and the host
timer interrupt handling cost, replacing them with a little math
(for guest->host TSC and host TSC->preemption timer conversion)
and a cheaper VMexit.  This benefits latency for isolated pCPUs.

[A word about performance... Yunhong reported a 30% reduction in average
 latency from cyclictest.  I made a similar test with tscdeadline_latency
 from kvm-unit-tests, and measured

 - ~20 clock cycles loss (out of ~3200, so less than 1% but still
   statistically significant) in the worst case where the test halts
   just after programming the TSC deadline timer

 - ~800 clock cycles gain (25% reduction in latency) in the best case
   where the test busy waits.

 I removed the VMX bits from Yunhong's patch, to concentrate them in the
 next patch - Paolo]
Signed-off-by: NYunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      ce7a058a
    • Y
      kvm: lapic: separate start_sw_tscdeadline from start_apic_timer · 53f9eedf
      由 Yunhong Jiang 提交于 
      The function to start the tsc deadline timer virtualization will be used
also by the pre_block hook when we use the preemption timer; change it
to a separate function. No logic changes.
Signed-off-by: NYunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      53f9eedf
  23. 19 5月, 2016 4 次提交
  25. 05 4月, 2016 1 次提交
    • L
      kvm: x86: make lapic hrtimer pinned · 61abdbe0
      由 Luiz Capitulino 提交于 
      When a vCPU runs on a nohz_full core, the hrtimer used by
the lapic emulation code can be migrated to another core.
When this happens, it's possible to observe milisecond
latency when delivering timer IRQs to KVM guests.

The huge latency is mainly due to the fact that
apic_timer_fn() expects to run during a kvm exit. It
sets KVM_REQ_PENDING_TIMER and let it be handled on kvm
entry. However, if the timer fires on a different core,
we have to wait until the next kvm exit for the guest
to see KVM_REQ_PENDING_TIMER set.

This problem became visible after commit 9642d18e. This
commit changed the timer migration code to always attempt
to migrate timers away from nohz_full cores. While it's
discussable if this is correct/desirable (I don't think
it is), it's clear that the lapic emulation code has
a requirement on firing the hrtimer in the same core
where it was started. This is achieved by making the
hrtimer pinned.

Lastly, note that KVM has code to migrate timers when a
vCPU is scheduled to run in different core. However, this
forced migration may fail. When this happens, we can have
the same problem. If we want 100% correctness, we'll have
to modify apic_timer_fn() to cause a kvm exit when it runs
on a different core than the vCPU. Not sure if this is
possible.

Here's a reproducer for the issue being fixed:

 1. Set all cores but core0 to be nohz_full cores
 2. Start a guest with a single vCPU
 3. Trace apic_timer_fn() and kvm_inject_apic_timer_irqs()

You'll see that apic_timer_fn() will run in core0 while
kvm_inject_apic_timer_irqs() runs in a different core. If
you get both on core0, try running a program that takes 100%
of the CPU and pin it to core0 to force the vCPU out.
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      61abdbe0
  27. 03 3月, 2016 2 次提交
  29. 25 2月, 2016 1 次提交
    • M
      KVM: Use simple waitqueue for vcpu->wq · 8577370f
      由 Marcelo Tosatti 提交于 
      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-g0905f04e:

  ./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: NDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-4-git-send-email-wagi@monom.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
      8577370f
  31. 17 2月, 2016 1 次提交