From: "Raj, Ashok" <ashok.raj@intel.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
"Lan, Tianyu" <tianyu.lan@intel.com>,
"Peng, Chao P" <chao.p.peng@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"Hao, Xudong" <xudong.hao@intel.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Sun, Yi Y" <yi.y.sun@intel.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
Ashok Raj <ashok.raj@intel.com>
Subject: Re: [Qemu-devel] [RFC Design Doc v3] Enable Shared Virtual Memory feature in pass-through scenarios
Date: Wed, 1 Mar 2017 13:30:23 -0800 [thread overview]
Message-ID: <20170301213023.fv5utdpbh4zvsxdy@araj-mobl1> (raw)
In-Reply-To: <20170301210938.GE9043@char.us.ORACLE.com>
On Wed, Mar 01, 2017 at 04:09:38PM -0500, Konrad Rzeszutek Wilk wrote:
> .snip..
> >
> > No. SVM is purely about sharing CPU address space with device. Command
> > submission is still through kernel driver which controls rings (with SVM then
> > you can put VA into those commands). There are other vendor specific
> > features to enable direct user space submission which is orthogonal to SVM.
>
> Apologies for my ignorance but how is this beneficial? As in
> currently you would put in bus addresses on the ring, but now you
> can put VA addresses.
>
> The obvious benefit I see is that you omit the DMA ops which means there is
> less of 'lookup' (VA->bus address) in software - but I would have thought this
> would be negligible performance impact? And now the IOMMU alongside with
> the CPU would do this lookup.
>
> Or are there some other improvements in this?
Other benefits include,
- Application can simply pass its pointers to the SVM capable devices. which
means no memory registration overhead to get IO Virtual Addresses.
- No need to pin memory for DMA, since the devices can handle faults and
can request pages to be paged-in on demand.
>
> >
> > Thanks
> > Kevin
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
prev parent reply other threads:[~2017-03-01 21:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-30 8:49 [Qemu-devel] [RFC Design Doc v3] Enable Shared Virtual Memory feature in pass-through scenarios Liu, Yi L
2017-02-28 22:07 ` Konrad Rzeszutek Wilk
2017-03-01 6:51 ` Tian, Kevin
2017-03-01 21:09 ` Konrad Rzeszutek Wilk
2017-03-01 21:30 ` Raj, Ashok [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170301213023.fv5utdpbh4zvsxdy@araj-mobl1 \
--to=ashok.raj@intel.com \
--cc=chao.p.peng@intel.com \
--cc=iommu@lists.linux-foundation.org \
--cc=jacob.jun.pan@intel.com \
--cc=kevin.tian@intel.com \
--cc=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=qemu-devel@nongnu.org \
--cc=tianyu.lan@intel.com \
--cc=xudong.hao@intel.com \
--cc=yi.y.sun@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).