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

[Jan Kiszka <jan.kiszka@siemens.com>]

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.
> 
> 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 */

Doesn't this comment belong to the block above?

> +		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) {

Jan

-- 
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