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

[Gleb Natapov <gleb@redhat.com>]

On Wed, Feb 20, 2013 at 05:48:40PM +0100, Jan Kiszka wrote:
> On 2013-02-20 17:46, Gleb Natapov wrote:
> > On Wed, Feb 20, 2013 at 02:01:47PM +0100, 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.
> >>
> >>  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;
> > Why is this needed here?
> 
> Please check if my reply to Nadav explains this sufficiently.
> 
Ah, sorry. Will follow up there if it is not.

--
			Gleb.