2017-09-29 01:16:51

by Wanpeng Li

Subject: [PATCH RESEND] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume

From: Wanpeng Li <[email protected]>

------------[ 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 <[email protected]>
Cc: Radim Krčmář <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
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 c83d28b..1ca91c8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9840,7 +9840,8 @@ 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 |
--
2.7.4

2017-09-29 14:32:59

by Paolo Bonzini

Subject: Re: [PATCH RESEND] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume

On 29/09/2017 03:16, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> ------------[ 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 <[email protected]>
> Cc: Radim Krčmář <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> 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 c83d28b..1ca91c8 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -9840,7 +9840,8 @@ 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 |
>

Thanks, I guess that's better than nothing for now!

Paolo