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Re: [Qemu-devel] [PATCH for-2.11] intel_iommu: fix missing BQL in pt fas
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH for-2.11] intel_iommu: fix missing BQL in pt fast path |
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Date: |
Fri, 18 Aug 2017 18:06:17 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 18/08/2017 06:02, Peter Xu wrote:
>> The patch below is okay. However, vtd_switch_address_space is
>> expensive, which is why I suggested the bottom half.
> But still, shall we just do it this way? It looks cleaner.
>
> For the slowness (as I mentioned below), one thing to mention is that,
> this fast path should even not be used when PT is enabled. When
> "iommu=pt" is set, the IOMMU regions are off start from the very
> beginning. In other words, this patch should only affect a very
> corner use case, and to make sure that use case is safe, though it
> brings the first IO of that use case slower.
>
> How do you think?
Sure, the patch you posted is fine by me.
Paolo