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  1. Jul 05, 2016
  3. Jul 01, 2016
    • Wanpeng Li's avatar
      KVM: vmx: fix missed cancellation of TSC deadline timer · 196f20ca
      Wanpeng Li authored 
      

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: default avatarWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      196f20ca
    • Wanpeng Li's avatar
      KVM: x86: introduce cancel_hv_tscdeadline · bd97ad0e
      Wanpeng Li authored 
      

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: default avatarWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      bd97ad0e
    • Paolo Bonzini's avatar
      KVM: vmx: fix underflow in TSC deadline calculation · 9175d2e9
      Paolo Bonzini authored 
      

If the TSC deadline timer is programmed really close to the deadline or
even in the past, the computation in vmx_set_hv_timer can underflow and
cause delta_tsc to be set to a huge value.  This generally results
in vmx_set_hv_timer returning -ERANGE, but we can fix it by limiting
delta_tsc to be positive or zero.

Reported-by: default avatarWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      9175d2e9
    • Paolo Bonzini's avatar
      KVM: x86: use guest_exit_irqoff · f2485b3e
      Paolo Bonzini authored 
      

This gains a few clock cycles per vmexit.  On Intel there is no need
anymore to enable the interrupts in vmx_handle_external_intr, since
we are using the "acknowledge interrupt on exit" feature.  AMD
needs to do that, and must be careful to avoid the interrupt shadow.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      f2485b3e
    • Paolo Bonzini's avatar
      KVM: x86: always use "acknowledge interrupt on exit" · 91fa0f8e
      Paolo Bonzini authored 
      

This is necessary to simplify handle_external_intr in the next patch.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      91fa0f8e
    • Paolo Bonzini's avatar
      KVM: remove kvm_guest_enter/exit wrappers · 6edaa530
      Paolo Bonzini authored 
      

Use the functions from context_tracking.h directly.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      6edaa530
  5. Jun 28, 2016
  7. Jun 24, 2016
  9. Jun 21, 2016