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Date: Wed, 13 Sep 2017 23:45:48 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org Cc: Radim Krčmář <rkrcmar@...hat.com>, Wanpeng Li <wanpeng.li@...mail.com> Subject: Re: [PATCH 1/2] KVM: nVMX: Fix nested #PF intends to break L1's vmlauch/vmresume On 13/09/2017 13:03, Wanpeng Li wrote: > From: Wanpeng Li <wanpeng.li@...mail.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@...hat.com> > Cc: Radim Krčmář <rkrcmar@...hat.com> > Signed-off-by: Wanpeng Li <wanpeng.li@...mail.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. Paolo
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