linux-kernel - Re: [RFC PATCH 16/18] KVM: add kvm_arch_vcpu_prevent_run to prevent VM ENTER when NMI is received

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Message-ID: <4FEC8AFB.8060606@redhat.com>
Date:	Thu, 28 Jun 2012 19:48:59 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	yrl.pp-manager.tt@...achi.com,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC PATCH 16/18] KVM: add kvm_arch_vcpu_prevent_run to prevent
 VM ENTER when NMI is received

On 06/28/2012 09:08 AM, Tomoki Sekiyama wrote:
> Since NMI can not be disabled around VM enter, there is a race between
> receiving NMI to kick a guest and entering the guests on slave CPUs.If the
> NMI is received just before entering VM, after the NMI handler is invoked,
> it continues entering the guest and the effect of the NMI will be lost.
> 
> This patch adds kvm_arch_vcpu_prevent_run(), which causes VM exit right
> after VM enter. The NMI handler uses this to ensure the execution of the
> guest is cancelled after NMI.
> 
>  
> +/*
> + * Make VMRESUME fail using preemption timer with timer value = 0.
> + * On processors that doesn't support preemption timer, VMRESUME will fail
> + * by internal error.
> + */
> +static void vmx_prevent_run(struct kvm_vcpu *vcpu, int prevent)
> +{
> +	if (prevent)
> +		vmcs_set_bits(PIN_BASED_VM_EXEC_CONTROL,
> +			      PIN_BASED_PREEMPTION_TIMER);
> +	else
> +		vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL,
> +				PIN_BASED_PREEMPTION_TIMER);
> +}

This may interrupt another RMW sequence, which will then overwrite the
control.  So it needs to be called only if inside the entry sequence
(otherwise can just set a KVM_REQ_IMMEDIATE_EXIT in vcpu->requests).

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


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