Re: [PATCH] KVM: nVMX: Rework event injection and recovery

[Gleb Natapov <gleb@redhat.com>]

On Wed, Feb 20, 2013 at 03:53:53PM +0100, Jan Kiszka wrote:
> On 2013-02-20 14:01, Jan Kiszka wrote:
> > This aligns VMX more with SVM regarding event injection and recovery for
> > nested guests. The changes allow to inject interrupts directly from L0
> > to L2.
> > 
> > One difference to SVM is that we always transfer the pending event
> > injection into the architectural state of the VCPU and then drop it from
> > there if it turns out that we left L2 to enter L1.
> > 
> > VMX and SVM are now identical in how they recover event injections from
> > unperformed vmlaunch/vmresume: We detect that VM_ENTRY_INTR_INFO_FIELD
> > still contains a valid event and, if yes, transfer the content into L1's
> > idt_vectoring_info_field.
> > 
> > To avoid that we incorrectly leak an event into the architectural VCPU
> > state that L1 wants to inject, we skip cancellation on nested run.
> > 
> > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > ---
> > 
> > Survived moderate testing here and (currently) makes sense to me, but
> > please review very carefully. I wouldn't be surprised if I'm still
> > missing some subtle corner case.
> 
> Forgot to point this out again: It still takes "KVM: nVMX: Fix injection
> of PENDING_INTERRUPT and NMI_WINDOW exits to L1" to make L0->L2
> injection work. So this patch logically depends on it.
> 
But this patch has hunks from that patch.

> Jan
> 
> > 
> >  arch/x86/kvm/vmx.c |   57 +++++++++++++++++++++++----------------------------
> >  1 files changed, 26 insertions(+), 31 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index dd3a8a0..7d2fbd2 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -6489,8 +6489,6 @@ static void __vmx_complete_interrupts(struct vcpu_vmx *vmx,
> >  
> >  static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
> >  {
> > -	if (is_guest_mode(&vmx->vcpu))
> > -		return;
> >  	__vmx_complete_interrupts(vmx, vmx->idt_vectoring_info,
> >  				  VM_EXIT_INSTRUCTION_LEN,
> >  				  IDT_VECTORING_ERROR_CODE);
> > @@ -6498,7 +6496,7 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
> >  
> >  static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
> >  {
> > -	if (is_guest_mode(vcpu))
> > +	if (to_vmx(vcpu)->nested.nested_run_pending)
> >  		return;
> >  	__vmx_complete_interrupts(to_vmx(vcpu),
> >  				  vmcs_read32(VM_ENTRY_INTR_INFO_FIELD),
> > @@ -6531,21 +6529,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> >  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> >  	unsigned long debugctlmsr;
> >  
> > -	if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
> > -		struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> > -		if (vmcs12->idt_vectoring_info_field &
> > -				VECTORING_INFO_VALID_MASK) {
> > -			vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
> > -				vmcs12->idt_vectoring_info_field);
> > -			vmcs_write32(VM_ENTRY_INSTRUCTION_LEN,
> > -				vmcs12->vm_exit_instruction_len);
> > -			if (vmcs12->idt_vectoring_info_field &
> > -					VECTORING_INFO_DELIVER_CODE_MASK)
> > -				vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
> > -					vmcs12->idt_vectoring_error_code);
> > -		}
> > -	}
> > -
> >  	/* Record the guest's net vcpu time for enforced NMI injections. */
> >  	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
> >  		vmx->entry_time = ktime_get();
> > @@ -6704,17 +6687,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
> >  
> >  	vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
> >  
> > -	if (is_guest_mode(vcpu)) {
> > -		struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> > -		vmcs12->idt_vectoring_info_field = vmx->idt_vectoring_info;
> > -		if (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK) {
> > -			vmcs12->idt_vectoring_error_code =
> > -				vmcs_read32(IDT_VECTORING_ERROR_CODE);
> > -			vmcs12->vm_exit_instruction_len =
> > -				vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
> > -		}
> > -	}
> > -
> >  	vmx->loaded_vmcs->launched = 1;
> >  
> >  	vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
> > @@ -7403,9 +7375,32 @@ void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
> >  	vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
> >  	vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
> >  
> > -	/* clear vm-entry fields which are to be cleared on exit */
> > -	if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
> > +	/* drop what we picked up for L0 via vmx_complete_interrupts */
> > +	vcpu->arch.nmi_injected = false;
> > +	kvm_clear_exception_queue(vcpu);
> > +	kvm_clear_interrupt_queue(vcpu);
> > +
> > +	if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) &&
> > +	    vmcs12->vm_entry_intr_info_field & INTR_INFO_VALID_MASK) {
> > +		/*
> > +		 * Preserve the event that was supposed to be injected
> > +		 * by emulating it would have been returned in
> > +		 * IDT_VECTORING_INFO_FIELD.
> > +		 */
> > +		if (vmcs_read32(VM_ENTRY_INTR_INFO_FIELD) &
> > +		    INTR_INFO_VALID_MASK) {
> > +			vmcs12->idt_vectoring_info_field =
> > +				vmcs12->vm_entry_intr_info_field;
> > +			vmcs12->idt_vectoring_error_code =
> > +				vmcs12->vm_entry_exception_error_code;
> > +			vmcs12->vm_exit_instruction_len =
> > +				vmcs12->vm_entry_instruction_len;
> > +			vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);
> > +		}
> > +
> > +		/* clear vm-entry fields which are to be cleared on exit */
> >  		vmcs12->vm_entry_intr_info_field &= ~INTR_INFO_VALID_MASK;
> > +	}
> >  }
> >  
> >  /*
> > 
> -- 
> Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
> Corporate Competence Center Embedded Linux

--
			Gleb.