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Date: Fri, 4 May 2012 17:14:49 +0530
From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>
Cc: peterz@infradead.org, mingo@elte.hu, jeremy@goop.org, mtosatti@redhat.com,
        kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org,
        avi@redhat.com, hpa@zytor.com
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others
Message-ID: <20120504114449.GB25659@linux.vnet.ibm.com>
Reply-To: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
References: <20120427161727.27082.43096.stgit@abhimanyu>
 <20120427162401.27082.59387.stgit@abhimanyu>
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* Nikunj A. Dadhania <nikunj@linux.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