linux-kernel - Re: [PATCH] KVM: x86: fix missed memory synchronization when patch hypercall

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Date:	Sun, 09 Jun 2013 17:29:37 +0800
From:	Xiao Guangrong <xiaoguangrong.eric@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Paolo Bonzini <pbonzini@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: fix missed memory synchronization when patch
 hypercall

On 06/09/2013 04:45 PM, Gleb Natapov wrote:

> +static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt)
> +{
> +	struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
> +	return kvm_exec_with_stopped_vcpu(vcpu->kvm,
> +			emulator_fix_hypercall_cb, ctxt);
> +}
> +
> +
>  /*
>   * Check if userspace requested an interrupt window, and that the
>   * interrupt window is open.
> @@ -5761,6 +5769,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  			kvm_deliver_pmi(vcpu);
>  		if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu))
>  			vcpu_scan_ioapic(vcpu);
> +		if (kvm_check_request(KVM_REQ_STOP_VCPU, vcpu)){
> +			mutex_lock(&vcpu->kvm->lock);
> +			mutex_unlock(&vcpu->kvm->lock);

We should execute a serializing instruction here?

> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -222,6 +222,18 @@ void kvm_make_scan_ioapic_request(struct kvm *kvm)
>  	make_all_cpus_request(kvm, KVM_REQ_SCAN_IOAPIC);
>  }
> 
> +int kvm_exec_with_stopped_vcpu(struct kvm *kvm, int (*cb)(void *), void *data)
> +{
> +	int r;
> +
> +	mutex_lock(&kvm->lock);
> +	make_all_cpus_request(kvm, KVM_REQ_STOP_VCPU);
> +	r = cb(data);

And here?

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