Re: buggy emulate_int_real

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-04-13 00:39, Serge E. Hallyn wrote:
> Quoting Serge E. Hallyn (serge@hallyn.com):
>> Quoting Jan Kiszka (jan.kiszka@web.de):
>>> From a brief refresh-reading, I would say
>>>
>>> if (interrupt.soft || kvm_exception_is_soft(nr))
>>>     increment_eip_by_inst_len
>>>
>>> but only for those interrupts/exceptions which were raised by the
>>> triggering instructions, _not_ for exceptions raise while processing
>>> them (e.g. a page fault while accessing the IDT).
>>>
>>> Jan
>>
>> Ok, thanks guys.  I'm currently trying a compile of the following.
> 
> With the obvious fixes, that turns into the below, which seems to be
> working for me:
> 
> From 555696f355ec2db9f4919f5e363355a2671b15a5 Mon Sep 17 00:00:00 2001
> From: Serge E. Hallyn <serge.hallyn@canonical.com>
> Date: Tue, 12 Apr 2011 22:18:40 +0100
> Subject: [PATCH 1/1] kvm: fix push of wrong eip when doing softint
> 
> When doing a soft int, we need to bump eip before pushing it to
> the stack.  Otherwise we'll do the int a second time.
> 
> Signed-off-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
> ---
>  arch/x86/kvm/vmx.c |   12 +++++++++---
>  arch/x86/kvm/x86.c |    3 ++-
>  arch/x86/kvm/x86.h |    2 +-
>  3 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index bf89ec2..3aad96c 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1053,7 +1053,10 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
>  	}
>  
>  	if (vmx->rmode.vm86_active) {
> -		if (kvm_inject_realmode_interrupt(vcpu, nr) != EMULATE_DONE)
> +		int inc_eip = 0;
> +		if (kvm_exception_is_soft(nr))
> +			inc_eip = vcpu->arch.event_exit_inst_len;
> +		if (kvm_inject_realmode_interrupt(vcpu, nr, inc_eip) != EMULATE_DONE)
>  			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>  		return;
>  	}
> @@ -2871,7 +2874,10 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
>  
>  	++vcpu->stat.irq_injections;
>  	if (vmx->rmode.vm86_active) {
> -		if (kvm_inject_realmode_interrupt(vcpu, irq) != EMULATE_DONE)
> +		int inc_eip = 0;
> +		if (vcpu->arch.interrupt.soft)
> +			inc_eip = vcpu->arch.event_exit_inst_len;
> +		if (kvm_inject_realmode_interrupt(vcpu, irq, inc_eip) != EMULATE_DONE)
>  			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>  		return;
>  	}
> @@ -2905,7 +2911,7 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
>  
>  	++vcpu->stat.nmi_injections;
>  	if (vmx->rmode.vm86_active) {
> -		if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR) != EMULATE_DONE)
> +		if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR, 0) != EMULATE_DONE)
>  			kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>  		return;
>  	}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bcc0efc..8911622 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4293,7 +4293,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
>  	memcpy(c->regs, vcpu->arch.regs, sizeof c->regs);
>  }
>  
> -int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq)
> +int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
>  {
>  	struct decode_cache *c = &vcpu->arch.emulate_ctxt.decode;
>  	int ret;
> @@ -4303,6 +4303,7 @@ int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq)
>  	vcpu->arch.emulate_ctxt.decode.op_bytes = 2;
>  	vcpu->arch.emulate_ctxt.decode.ad_bytes = 2;
>  	vcpu->arch.emulate_ctxt.decode.eip = vcpu->arch.emulate_ctxt.eip;
> +	vcpu->arch.emulate_ctxt.decode.eip += inc_eip;

I would fold this into the previous line.

>  	ret = emulate_int_real(&vcpu->arch.emulate_ctxt, &emulate_ops, irq);
>  
>  	if (ret != X86EMUL_CONTINUE)
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index c600da8..e407ed3 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -77,7 +77,7 @@ static inline u32 bit(int bitno)
>  
>  void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
>  void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
> -int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq);
> +int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
>  
>  void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
>  

Looks consistent to me.

Jan


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