-----Original Message-----
From: Jason Gunthorpe [mailto:jgg@ziepe.ca]
Sent: Tuesday, February 2, 2021 12:44 PM
To: Tian, Kevin <kevin.tian@intel.com>
Cc: Song Bao Hua (Barry Song) <redacted>; chensihang (A)
[off-list ref]; Arnd Bergmann [off-list ref]; Greg
Kroah-Hartman [off-list ref]; linux-kernel@vger.kernel.org;
iommu@lists.linux-foundation.org; linux-mm@kvack.org; Zhangfei Gao
[off-list ref]; Liguozhu (Kenneth) [off-list ref];
linux-accelerators@lists.ozlabs.org
Subject: Re: [RFC PATCH v2] uacce: Add uacce_ctrl misc device

On Fri, Jan 29, 2021 at 10:09:03AM +0000, Tian, Kevin wrote:

quoted

quoted

SVA is not doom to work with IO page fault only. If we have SVA+pin,
we would get both sharing address and stable I/O latency.

Isn't it like a traditional MAP_DMA API (imply pinning) plus specifying
cpu_va of the memory pool as the iova?

I think their issue is the HW can't do the cpu_va trick without also
involving the system IOMMU in a SVA mode

It really is something that belongs under some general /dev/sva as we
talked on the vfio thread

AFAIK, there is no this /dev/sva so /dev/uacce is an uAPI
which belongs to sva.

Another option is that we add a system call like
fs/userfaultfd.c, and move the file_operations and  ioctl
to the anon inode by creating fd via anon_inode_getfd().
Then nothing will be buried by uacce.

Jason

Thanks
Barry