linux-kernel - Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb

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Date:	Fri, 4 May 2012 17:14:49 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>
Cc:	peterz@...radead.org, mingo@...e.hu, jeremy@...p.org,
	mtosatti@...hat.com, kvm@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, hpa@...or.com
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others

* Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com> [2012-04-27 21:54:37]:

> @@ -1549,6 +1549,11 @@ static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
>  		return;
> 
>  	vs->state = 1;
> +	if (vs->flush_on_enter) {
> +		kvm_mmu_flush_tlb(vcpu);
> +		vs->flush_on_enter = 0;
> +	}
> +
>  	kvm_write_guest_cached(vcpu->kvm, ghc, vs, 2*sizeof(__u32));

Reading flush_on_enter before writing ->state (=1) is racy afaics (and
may cause vcpu to miss a TLB flush request).

- vatsa

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