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Re: [Qemu-devel] [PATCH v6 1/3] IOMMU: add option to enable VTD_CAP_CM t

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH v6 1/3] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest
Date: Fri, 11 Nov 2016 10:32:42 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 2016年11月10日 06:00, Michael S. Tsirkin wrote:
On Wed, Nov 09, 2016 at 03:28:02PM +0800, Jason Wang wrote:
>On 2016年11月08日 19:04, Aviv B.D wrote:
> >From: "Aviv Ben-David"<address@hidden>
> >
> >This capability asks the guest to invalidate cache before each map operation.
> >We can use this invalidation to trap map operations in the hypervisor.
>Like I've asked twice in the past, I want to know why don't you cache
>translation faults as what spec required (especially this is a guest visible
>Btw, please cc me on posting future versions.
Caching isn't guest visible.

Seems not, if one fault mapping were cached by IOTLB. Guest can notice this behavior.

Spec just says you*can*  cache,
not that you must.

Yes, but what did in this patch is "don't". What I suggest is just a "can", since anyway the IOTLB entries were limited and could be replaced by other.


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