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KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume
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------------[ cut here ]------------
 WARNING: CPU: 4 PID: 5280 at /home/kernel/linux/arch/x86/kvm//vmx.c:11394 nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel]
 CPU: 4 PID: 5280 Comm: qemu-system-x86 Tainted: G        W  OE   4.13.0+ torvalds#17
 RIP: 0010:nested_vmx_vmexit+0xc2b/0xd70 [kvm_intel]
 Call Trace:
  ? emulator_read_emulated+0x15/0x20 [kvm]
  ? segmented_read+0xae/0xf0 [kvm]
  vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel]
  ? vmx_inject_page_fault_nested+0x60/0x70 [kvm_intel]
  x86_emulate_instruction+0x733/0x810 [kvm]
  vmx_handle_exit+0x2f4/0xda0 [kvm_intel]
  ? kvm_arch_vcpu_ioctl_run+0xd2f/0x1c60 [kvm]
  kvm_arch_vcpu_ioctl_run+0xdab/0x1c60 [kvm]
  ? kvm_arch_vcpu_load+0x62/0x230 [kvm]
  kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? __fget+0xfc/0x210
  do_vfs_ioctl+0xa4/0x6a0
  ? __fget+0x11d/0x210
  SyS_ioctl+0x79/0x90
  entry_SYSCALL_64_fastpath+0x23/0xc2

A nested #PF is triggered during L0 emulating instruction for L2. However, it
doesn't consider we should not break L1's vmlauch/vmresme. This patch fixes
it by queuing the #PF exception instead ,requesting an immediate VM exit from
L2 and keeping the exception for L1 pending for a subsequent nested VM exit.

This should actually work all the time, making vmx_inject_page_fault_nested
totally unnecessary.  However, that's not working yet, so this patch can work
around the issue in the meanwhile.

Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
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@bonzini
Wanpeng Li authored and bonzini committed Sep 29, 2017
1 parent c0a1666 commit 305d0ab
Showing 1 changed file with 2 additions and 1 deletion.
3 changes: 2 additions & 1 deletion arch/x86/kvm/vmx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9845,7 +9845,8 @@ static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,

WARN_ON(!is_guest_mode(vcpu));

if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code)) {
if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code) &&
!to_vmx(vcpu)->nested.nested_run_pending) {
vmcs12->vm_exit_intr_error_code = fault->error_code;
nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
PF_VECTOR | INTR_TYPE_HARD_EXCEPTION |
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