Re: [PATCH 2/2] KVM: VMX: Fix guest debugging while in L2

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/02/2016 20:15, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> When we take a #DB or #BP vmexit while in guest mode, we first of all
> need to check if there is ongoing guest debugging that might be
> interested in the event. Currently, we unconditionally leave L2 and
> inject the event into L1 if it is intercepting the exceptions. That
> breaks things marvelously.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  arch/x86/kvm/vmx.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 7852092..cb501d3 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -968,6 +968,16 @@ static inline bool is_exception_n(u32 intr_info, u8 vector)
>  		(INTR_TYPE_HARD_EXCEPTION | vector | INTR_INFO_VALID_MASK);
>  }
> 
> +static inline bool is_debug(u32 intr_info)
> +{
> +	return is_exception_n(intr_info, DB_VECTOR);
> +}
> +
> +static inline bool is_breakpoint(u32 intr_info)
> +{
> +	return is_exception_n(intr_info, BP_VECTOR);
> +}
> +
>  static inline bool is_page_fault(u32 intr_info)
>  {
>  	return is_exception_n(intr_info, PF_VECTOR);
> @@ -7753,6 +7763,13 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
>  		else if (is_no_device(intr_info) &&
>  			 !(vmcs12->guest_cr0 & X86_CR0_TS))
>  			return false;
> +		else if (is_debug(intr_info) &&
> +			 vcpu->guest_debug &
> +			 (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
> +			return false;
> +		else if (is_breakpoint(intr_info) &&
> +			 vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
> +			return false;
>  		return vmcs12->exception_bitmap &
>  				(1u << (intr_info & INTR_INFO_VECTOR_MASK));
>  	case EXIT_REASON_EXTERNAL_INTERRUPT:
> 

Thanks, I'll apply both patches shortly to kvm/queue.

However, next time please do not sign the patches.  git send-email
doesn't like the way PGP signed messages escape "-" at the beginning of
the line.

Paolo