Re: [PATCH 2/5] Don't call svm_complete_interrupts for nested guests

[Joerg Roedel <joro@8bytes.org>]

On Fri, Sep 18, 2009 at 03:00:29PM +0200, Alexander Graf wrote:
> SVM has some cleanup code, that tries to reinject interrupts and exceptions
> when the guest didn't manage to deal with them yet. It basically transfers
> them to KVM internal state.
> 
> Unfortunately, the internal state is reserved for the L1 guest state, so we
> shouldn't try to go through that logic when running a nested guest.
> 
> When doing something the host KVM can handle, let's just reinject the event
> into the L2 guest, because we didn't touch its state anyways.

I don't really understandt what problem this patch addresses. There are
situations where we have events to reinject into the l2 guest directly.
But the generic reinjection code works fine for it.
The only problematic thing with it is that it implicitly relies on
exit_int_info not to be changed in the exit cycle (which would be worth
a comment).

	Joerg

> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/x86/kvm/svm.c |   18 ++++++++++++++----
>  1 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f12a669..61efd13 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2349,7 +2349,10 @@ static int handle_exit(struct kvm_vcpu *vcpu)
>  	trace_kvm_exit(exit_code, svm->vmcb->save.rip);
>  
>  	if (is_nested(svm)) {
> +		struct vmcb_control_area *control = &svm->vmcb->control;
>  		int vmexit;
> +		int type;
> +		int vec;
>  
>  		nsvm_printk("nested handle_exit: 0x%x | 0x%lx | 0x%lx | 0x%lx\n",
>  			    exit_code, svm->vmcb->control.exit_info_1,
> @@ -2362,9 +2365,18 @@ static int handle_exit(struct kvm_vcpu *vcpu)
>  
>  		if (vmexit == NESTED_EXIT_DONE)
>  			return 1;
> -	}
>  
> -	svm_complete_interrupts(svm);
> +		type = control->exit_int_info & SVM_EXITINTINFO_TYPE_MASK;
> +		vec = control->exit_int_info & SVM_EXITINTINFO_VEC_MASK;
> +		if ((type == SVM_EXITINTINFO_TYPE_INTR) ||
> +		    ((type == SVM_EXITINTINFO_TYPE_EXEPT) && !kvm_exception_is_soft(vec))) {
> +			control->event_inj = control->exit_int_info;
> +			control->event_inj_err = control->exit_int_info_err;
> +		}
> +	} else {
> +		/* Don't interpret exit_info for nested guests */
> +		svm_complete_interrupts(svm);
> +	}
>  
>  	if (npt_enabled) {
>  		int mmu_reload = 0;
> @@ -2602,8 +2614,6 @@ static void svm_complete_interrupts(struct vcpu_svm *svm)
>  	case SVM_EXITINTINFO_TYPE_EXEPT:
>  		/* In case of software exception do not reinject an exception
>  		   vector, but re-execute and instruction instead */
> -		if (is_nested(svm))
> -			break;
>  		if (kvm_exception_is_soft(vector))
>  			break;
>  		if (exitintinfo & SVM_EXITINTINFO_VALID_ERR) {
> -- 
> 1.6.0.2
> 
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