From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
"chensihang (A)" <chensihang1@hisilicon.com>,
Arnd Bergmann <arnd@arndb.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Zhangfei Gao <zhangfei.gao@linaro.org>,
"Liguozhu (Kenneth)" <liguozhu@hisilicon.com>,
"linux-accelerators@lists.ozlabs.org"
<linux-accelerators@lists.ozlabs.org>
Subject: RE: [RFC PATCH v2] uacce: Add uacce_ctrl misc device
Date: Tue, 2 Feb 2021 02:51:30 +0000 [thread overview]
Message-ID: <MWHPR11MB1886464FFEF10DF9AE708C4A8CB59@MWHPR11MB1886.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20210201234424.GI4718@ziepe.ca>
> From: Jason Gunthorpe <jgg@ziepe.ca>
> Sent: Tuesday, February 2, 2021 7:44 AM
>
> On Fri, Jan 29, 2021 at 10:09:03AM +0000, Tian, Kevin wrote:
> > > 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
>
This is the part that I didn't understand. Using cpu_va in a MAP_DMA
interface doesn't require device support. It's just an user-specified
address to be mapped into the IOMMU page table. On the other hand,
sharing CPU page table through a SVA interface for an usage where I/O
page faults must be completely avoided seems a misleading attempt.
Even if people do want this model (e.g. mix pinning+fault), it should be
a mm syscall as Greg pointed out, not specific to sva.
Thanks
Kevin
next prev parent reply other threads:[~2021-02-02 2:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 8:34 [RFC PATCH v2] uacce: Add uacce_ctrl misc device Zhou Wang
2021-01-25 9:28 ` Greg Kroah-Hartman
2021-01-25 12:47 ` Zhou Wang
2021-01-25 15:47 ` Jason Gunthorpe
2021-01-25 22:21 ` Song Bao Hua (Barry Song)
2021-01-25 23:16 ` Jason Gunthorpe
2021-01-25 23:35 ` Song Bao Hua (Barry Song)
2021-01-26 1:13 ` Jason Gunthorpe
2021-01-26 1:26 ` Song Bao Hua (Barry Song)
2021-01-26 18:20 ` Jason Gunthorpe
2021-01-28 1:28 ` Song Bao Hua (Barry Song)
[not found] ` <MWHPR11MB1886DC78C5FBA3636B94F2578CB99@MWHPR11MB1886.namprd11.prod.outlook.com>
2021-02-01 23:44 ` Jason Gunthorpe
2021-02-02 0:22 ` Song Bao Hua (Barry Song)
2021-02-02 2:51 ` Tian, Kevin [this message]
2021-02-02 3:47 ` Song Bao Hua (Barry Song)
2021-01-26 9:00 ` Zhou Wang
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