lkml.org 
[lkml]   [2017]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 1/2] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume
2017-09-14 7:14 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>:
> 2017-09-14 5:45 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>> On 13/09/2017 13:03, Wanpeng Li wrote:
>>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>>
>>> ------------[ 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+ #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.
>>>
>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>>> ---
>>> arch/x86/kvm/vmx.c | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index 4253ade..fda9dd6 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -9829,7 +9829,8 @@ 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 |
>>>
>>
>> Is vmx_inject_page_fault_nested even needed at all these days?
>>
>> kvm_inject_page_fault's call to kvm_queue_exception_e should transform
>> into an L2->L1 vmexit when vmx_check_nested_events is called.
>
> I saw L0 reboot/hang after do something like below:

Maybe something associated with which commit ef54bcfee (KVM: x86: skip
writeback on injection of nested exception) pointed out, IIUC,
fault->nested_page_fault will not be changed in
vmx_inject_page_fault_nested(), so we always return false in the case
of vcpu->arch.nested.mmu.inject_page_fault(), then the issue which the
commit try to avoid is encountered.

Regards,
Wanpeng Li

>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 4253ade..96b4f6f 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -9822,24 +9822,6 @@ static bool
> nested_vmx_is_page_fault_vmexit(struct vmcs12 *vmcs12,
> return inequality ^ bit;
> }
>
> -static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,
> - struct x86_exception *fault)
> -{
> - struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> -
> - WARN_ON(!is_guest_mode(vcpu));
> -
> - if (nested_vmx_is_page_fault_vmexit(vmcs12, fault->error_code)) {
> - vmcs12->vm_exit_intr_error_code = fault->error_code;
> - nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
> - PF_VECTOR | INTR_TYPE_HARD_EXCEPTION |
> - INTR_INFO_DELIVER_CODE_MASK |
> INTR_INFO_VALID_MASK,
> - fault->address);
> - } else {
> - kvm_inject_page_fault(vcpu, fault);
> - }
> -}
> -
> static inline bool nested_vmx_merge_msr_bitmap(struct kvm_vcpu *vcpu,
> struct vmcs12 *vmcs12);
>
> @@ -10654,7 +10636,7 @@ static int prepare_vmcs02(struct kvm_vcpu
> *vcpu, struct vmcs12 *vmcs12,
> return 1;
>
> if (!enable_ept)
> - vcpu->arch.walk_mmu->inject_page_fault =
> vmx_inject_page_fault_nested;
> + vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
>
> /*
>
> Regards,
> Wanpeng Li

\
 
 \ /
  Last update: 2017-09-14 19:28    [W:0.098 / U:6.352 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site