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From: | Jason Wang |
Subject: | Re: [Qemu-devel] [RFC] vhost-user: introduce F_NEED_ALL_IOTLB protocol feature |
Date: | Thu, 12 Apr 2018 11:56:37 +0800 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 |
On 2018年04月12日 11:37, Michael S. Tsirkin wrote:
Yeah, we are still using the existing IOTLB update messages to send the IOTLB messages to backend. The only difference is that, QEMU won't wait for the queries before sending the IOTLB update messages.Yes, my question is not very clear. I mean why must need a new feature bit? It looks to me qemu code can work without this. ThanksGenerally we avoid adding new messages without a protocol feature bit. While careful analysis might sometimes prove it's not a strict requirement, it's just overall a clean and robust approach.Right but the looks like the patch does not introduce any new type of messages. ThanksIn this case remote needs to know that it will send these messages. -- MST
Ok, if some backend does not expect qemu will send without any query from itself, I agree we need a new bit.
But it looks more like a workaround for buggy backend, at least vhost kernel does not need to know about this.
Thanks
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