linux-kernel - Re: [PATCH v2 2/3] KVM: x86: make exception_class() and exception

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Message-ID: <20190828183523.GC21651@linux.intel.com>
Date:   Wed, 28 Aug 2019 11:35:23 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jan Dakinevich <jan.dakinevich@...tuozzo.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Denis Lunev <den@...tuozzo.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] KVM: x86: make exception_class() and
 exception_type() globally visible

On Wed, Aug 28, 2019 at 05:02:57PM +0000, Jan Dakinevich wrote:
> exception_type() function was moved for upcoming sanity check in
> emulation code. exceptions_class() function is not supposed to be used
> right now, but it was moved as well to keep things together.

Doh, I didn't realize exception_type() was confined to x86.c when I
suggested the sanity check.  It'd probably be better to add the check
in x86_emulate_instruction and forego this patch, e.g.:

	if (ctxt->have_exception) {
		WARN_ON_ONCE(...);
		inject_emulated_exception(vcpu));
		return EMULATE_DONE;
	}

Arguably we shouldn't WARN on an unexpected vector until we actually try
to inject it anyways.

Sorry for the thrash.

> 
> Cc: Denis Lunev <den@...tuozzo.com>
> Cc: Roman Kagan <rkagan@...tuozzo.com>
> Cc: Denis Plotnikov <dplotnikov@...tuozzo.com>
> Signed-off-by: Jan Dakinevich <jan.dakinevich@...tuozzo.com>
> ---
>  arch/x86/kvm/x86.c | 46 ----------------------------------------------
>  arch/x86/kvm/x86.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 903fb7c..2b69ae0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -364,52 +364,6 @@ asmlinkage __visible void kvm_spurious_fault(void)
>  }
>  EXPORT_SYMBOL_GPL(kvm_spurious_fault);
>  
> -#define EXCPT_BENIGN		0
> -#define EXCPT_CONTRIBUTORY	1
> -#define EXCPT_PF		2
> -
> -static int exception_class(int vector)
> -{
> -	switch (vector) {
> -	case PF_VECTOR:
> -		return EXCPT_PF;
> -	case DE_VECTOR:
> -	case TS_VECTOR:
> -	case NP_VECTOR:
> -	case SS_VECTOR:
> -	case GP_VECTOR:
> -		return EXCPT_CONTRIBUTORY;
> -	default:
> -		break;
> -	}
> -	return EXCPT_BENIGN;
> -}
> -
> -#define EXCPT_FAULT		0
> -#define EXCPT_TRAP		1
> -#define EXCPT_ABORT		2
> -#define EXCPT_INTERRUPT		3
> -
> -static int exception_type(int vector)
> -{
> -	unsigned int mask;
> -
> -	if (WARN_ON(vector > 31 || vector == NMI_VECTOR))
> -		return EXCPT_INTERRUPT;
> -
> -	mask = 1 << vector;
> -
> -	/* #DB is trap, as instruction watchpoints are handled elsewhere */
> -	if (mask & ((1 << DB_VECTOR) | (1 << BP_VECTOR) | (1 << OF_VECTOR)))
> -		return EXCPT_TRAP;
> -
> -	if (mask & ((1 << DF_VECTOR) | (1 << MC_VECTOR)))
> -		return EXCPT_ABORT;
> -
> -	/* Reserved exceptions will result in fault */
> -	return EXCPT_FAULT;
> -}
> -
>  void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu)
>  {
>  	unsigned nr = vcpu->arch.exception.nr;
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index b5274e2..2b66347 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -369,4 +369,50 @@ static inline bool kvm_pat_valid(u64 data)
>  void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu);
>  void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu);
>  
> +#define EXCPT_BENIGN		0
> +#define EXCPT_CONTRIBUTORY	1
> +#define EXCPT_PF		2
> +
> +static inline int exception_class(int vector)
> +{
> +	switch (vector) {
> +	case PF_VECTOR:
> +		return EXCPT_PF;
> +	case DE_VECTOR:
> +	case TS_VECTOR:
> +	case NP_VECTOR:
> +	case SS_VECTOR:
> +	case GP_VECTOR:
> +		return EXCPT_CONTRIBUTORY;
> +	default:
> +		break;
> +	}
> +	return EXCPT_BENIGN;
> +}
> +
> +#define EXCPT_FAULT		0
> +#define EXCPT_TRAP		1
> +#define EXCPT_ABORT		2
> +#define EXCPT_INTERRUPT		3
> +
> +static inline int exception_type(int vector)
> +{
> +	unsigned int mask;
> +
> +	if (WARN_ON(vector > 31 || vector == NMI_VECTOR))
> +		return EXCPT_INTERRUPT;
> +
> +	mask = 1 << vector;
> +
> +	/* #DB is trap, as instruction watchpoints are handled elsewhere */
> +	if (mask & ((1 << DB_VECTOR) | (1 << BP_VECTOR) | (1 << OF_VECTOR)))
> +		return EXCPT_TRAP;
> +
> +	if (mask & ((1 << DF_VECTOR) | (1 << MC_VECTOR)))
> +		return EXCPT_ABORT;
> +
> +	/* Reserved exceptions will result in fault */
> +	return EXCPT_FAULT;
> +}
> +
>  #endif
> -- 
> 2.1.4
>