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Date: Thu, 09 May 2013 16:58:12 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] Vring: vring's listener's priority
 should higher than kvm
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To: liu ping fan <qemulist@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Liguori <anthony@codemonkey.ws>, "Michael S. Tsirkin" <mst@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

Il 09/05/2013 10:54, liu ping fan ha scritto:
> On Thu, May 9, 2013 at 4:44 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>> On Thu, May 09, 2013 at 08:40:21AM +0800, Liu Ping Fan wrote:
>>> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
>>>
>>> Hosts threads which handle vring should have high MemoryListener priority
>>> than kvm. For currently code, take the following scenario:
>>>   kvm_region_add() run earlier before vhost_region_add(), then in guest,
>>> vring's desc[i] can refer to addressX in the new region known by guest.
>>> But vhost does not know this new region yet, and the vring handler will
>>> fail.
>>>
>>> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
>>
>> Is this seen in testing, or are you describing a theorecitical
>> scenario? Please make this clear in the commit log.
>>
> A  theorecitical scenario.  I think vcpu thread and vhost are async,
> so we need this method to sync.

But why should this matter for hostmem?  It doesn't communicate in any
way with the hypervisor.

Paolo