linux-kernel - Re: [PATCH 03/10] KVM: SVM: Fix schedule-while-atomic on nested exception handling

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Message-ID: <4B7D4614.7040806@redhat.com>
Date:	Thu, 18 Feb 2010 15:52:20 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH 03/10] KVM: SVM: Fix schedule-while-atomic on nested exception
 handling

On 02/18/2010 01:38 PM, Joerg Roedel wrote:
> Move the actual vmexit routine out of code that runs with
> irqs and preemption disabled.
>
> Cc: stable@...nel.org
> Signed-off-by: Joerg Roedel<joerg.roedel@....com>
> ---
>   arch/x86/kvm/svm.c |   20 +++++++++++++++++---
>   1 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 7c96b8b..25d26ec 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -128,6 +128,7 @@ static void svm_flush_tlb(struct kvm_vcpu *vcpu);
>   static void svm_complete_interrupts(struct vcpu_svm *svm);
>
>   static int nested_svm_exit_handled(struct vcpu_svm *svm);
> +static int nested_svm_exit_handled_atomic(struct vcpu_svm *svm);
>   static int nested_svm_vmexit(struct vcpu_svm *svm);
>   static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
>   				      bool has_error_code, u32 error_code);
> @@ -1386,7 +1387,7 @@ static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
>   	svm->vmcb->control.exit_info_1 = error_code;
>   	svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
>
> -	return nested_svm_exit_handled(svm);
> +	return nested_svm_exit_handled_atomic(svm);
>   }
>    

What do you say to


    if (nested_svm_intercepts(svm))
         svm->nested.exit_required = true;

here, and recoding nested_svm_exit_handled() to call 
nested_svm_intercepts()?  I think it improves readability a little by 
avoiding a function that changes behaviour according to how it is called.

Long term, we may want to split out the big switch into the individual 
handlers, to avoid decoding the exit reason twice.

-- 
error compiling committee.c: too many arguments to function

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