• Wanpeng Li's avatar
    KVM: nVMX: Fix exception injection · be8c39b4
    Wanpeng Li authored
    commit d4912215 upstream.
    
     WARNING: CPU: 3 PID: 2840 at arch/x86/kvm/vmx.c:10966 nested_vmx_vmexit+0xdcd/0xde0 [kvm_intel]
     CPU: 3 PID: 2840 Comm: qemu-system-x86 Tainted: G           OE   4.12.0-rc3+ #23
     RIP: 0010:nested_vmx_vmexit+0xdcd/0xde0 [kvm_intel]
     Call Trace:
      ? kvm_check_async_pf_completion+0xef/0x120 [kvm]
      ? rcu_read_lock_sched_held+0x79/0x80
      vmx_queue_exception+0x104/0x160 [kvm_intel]
      ? vmx_queue_exception+0x104/0x160 [kvm_intel]
      kvm_arch_vcpu_ioctl_run+0x1171/0x1ce0 [kvm]
      ? kvm_arch_vcpu_load+0x47/0x240 [kvm]
      ? kvm_arch_vcpu_load+0x62/0x240 [kvm]
      kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
      ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
      ? __fget+0xf3/0x210
      do_vfs_ioctl+0xa4/0x700
      ? __fget+0x114/0x210
      SyS_ioctl+0x79/0x90
      do_syscall_64+0x81/0x220
      entry_SYSCALL64_slow_path+0x25/0x25
    
    This is triggered occasionally by running both win7 and win2016 in L2, in
    addition, EPT is disabled on both L1 and L2. It can't be reproduced easily.
    
    Commit 0b6ac343 (KVM: nVMX: Correct handling of exception injection) mentioned
    that "KVM wants to inject page-faults which it got to the guest. This function
    assumes it is called with the exit reason in vmcs02 being a #PF exception".
    Commit e011c663 (KVM: nVMX: Check all exceptions for intercept during delivery to
    L2) allows to check all exceptions for intercept during delivery to L2. However,
    there is no guarantee the exit reason is exception currently, when there is an
    external interrupt occurred on host, maybe a time interrupt for host which should
    not be injected to guest, and somewhere queues an exception, then the function
    nested_vmx_check_exception() will be called and the vmexit emulation codes will
    try to emulate the "Acknowledge interrupt on exit" behavior, the warning is
    triggered.
    
    Reusing the exit reason from the L2->L0 vmexit is wrong in this case,
    the reason must always be EXCEPTION_NMI when injecting an exception into
    L1 as a nested vmexit.
    
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Radim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: default avatarWanpeng Li <wanpeng.li@hotmail.com>
    Fixes: e011c663 ("KVM: nVMX: Check all exceptions for intercept during delivery to L2")
    Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    be8c39b4
vmx.c 308 KB