linux-kernel - Re: [PATCH] KVM: svm: support single stepping over emulated instructions

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Date:   Wed, 2 Aug 2017 22:13:38 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rkrcmar@...hat.com, me@...ehuey.com
Subject: Re: [PATCH] KVM: svm: support single stepping over emulated
 instructions

2017-08-02 18:03+0200, Paolo Bonzini:
> Use kvm_skip_emulated_instruction so that debug exceptions are
> properly injected.  This fixes debug.flat on AMD machines.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

We already have b742c1e6e79d ("KVM: SVM: handle singlestep exception
when skipping emulated instructions"), so the only applicable part of
this patch is

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0e846f0cb83b..931ba449456e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5548,6 +5548,7 @@ static void kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu, int *r)
>  		 */
>  		vcpu->arch.dr6 &= ~15;
>  		vcpu->arch.dr6 |= DR6_BS | DR6_RTM;
> +		kvm_update_dr6(vcpu);
>  		kvm_queue_exception(vcpu, DB_VECTOR);
>  	}
>  }

which makes sense.  And shouldn't we do the same for
kvm_vcpu_check_breakpoint()?

Thanks.