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Date:   Tue, 16 Jun 2020 08:22:12 -0700
From:   Jacob Pan <>
To:     Alex Williamson <>
        LKML <>,
        "Lu Baolu" <>,
        Joerg Roedel <>,
        David Woodhouse <>,
        Yi Liu <>,
        "Tian, Kevin" <>,
        Raj Ashok <>,
        "Christoph Hellwig" <>,
        Jean-Philippe Brucker <>,
        Eric Auger <>,
        Jonathan Corbet <>,
Subject: Re: [PATCH v2 1/3] docs: IOMMU user API

On Thu, 11 Jun 2020 17:27:27 -0700
Jacob Pan <> wrote:

> > 
> > But then I thought it even better if VFIO leaves the entire
> > copy_from_user() to the layer consuming it.
> >   
> OK. Sounds good, that was what Kevin suggested also. I just wasn't
> sure how much VFIO wants to inspect, I thought VFIO layer wanted to
> do a sanity check.
> Anyway, I will move copy_from_user to iommu uapi layer.

Just one more point brought up by Yi when we discuss this offline.

If we move copy_from_user to iommu uapi layer, then there will be
multiple copy_from_user calls for the same data when a VFIO container
has multiple domains, devices. For bind, it might be OK. But might be
additional overhead for TLB flush request from the guest.



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