linux-kernel - Re: [PATCH RFC] uaccess: user_access_begin_after_access

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Date:   Sat, 6 Jun 2020 16:08:27 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok()

On Fri, Jun 05, 2020 at 06:03:38PM +0800, Jason Wang wrote:
> 
> On 2020/6/5 上午12:49, Michael S. Tsirkin wrote:
> > > > 2. Second argument to translate_desc is a GPA, isn't it?
> > > No, it's IOVA, this function will be called only when IOTLB is enabled.
> > > 
> > > Thanks
> > Right IOVA. Point stands how does it make sense to cast
> > a userspace pointer to an IOVA? I guess it's just
> > because it's talking to qemu actually, so it's abusing
> > the notation a bit ...
> > 
> 
> Yes, but the issues are:
> 
> 1) VHOST_SET_VRING_ADDR is used for iotlb and !iotlb
> 2) so did the memory accessors
> 
> Unless we differ separate IOTLB datapath out, there's probably not easy to
> have another notation.
> 
> Thanks

With the batching/format independence rework, it might be possible to
separate that down the road. We'll see.

-- 
MST