linux-kernel - Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio generation number

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Message-ID: <CALzav=eZyM4_Y6yVoDnTZZUEbbF+T8WR_mSZa3h51FHs1uGBWQ@mail.gmail.com>
Date:	Tue, 12 Aug 2014 14:18:45 -0700
From:	David Matlack <dmatlack@...gle.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	gleb@...hat.com, avi.kivity@...il.com, mtosatti@...hat.com,
	Paolo Bonzini <pbonzini@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio
 generation number

On Mon, Aug 11, 2014 at 10:02 PM, Xiao Guangrong
<xiaoguangrong@...ux.vnet.ibm.com> wrote:
> @@ -722,9 +719,10 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
>  {
>         struct kvm_memslots *old_memslots = kvm->memslots;
>

I think you want

  slots->generation = old_memslots->generation;

here.

On the KVM_MR_DELETE path, install_new_memslots is called twice so this
patch introduces a short window of time where the generation number
actually decreases.

> -       update_memslots(slots, new, kvm->memslots->generation);
> +       update_memslots(slots, new);
>         rcu_assign_pointer(kvm->memslots, slots);
>         synchronize_srcu_expedited(&kvm->srcu);
> +       slots->generation++;
>
>         kvm_arch_memslots_updated(kvm);
>
> --
> 1.8.3.1
>
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