From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gregory Haskins <gregory.haskins@gmail.com>
Cc: Avi Kivity <avi@redhat.com>,
"Ira W. Snyder" <iws@ovro.caltech.edu>,
netdev@vger.kernel.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org,
akpm@linux-foundation.org, hpa@zytor.com,
Rusty Russell <rusty@rustcorp.com.au>,
s.hetze@linux-ag.com, alacrityvm-devel@lists.sourceforge.net
Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server
Date: Tue, 15 Sep 2009 17:28:21 +0300 [thread overview]
Message-ID: <20090915142821.GA24488@redhat.com> (raw)
In-Reply-To: <4AAF9BAF.3030109@gmail.com>
On Tue, Sep 15, 2009 at 09:50:39AM -0400, Gregory Haskins wrote:
> Avi Kivity wrote:
> > On 09/15/2009 04:03 PM, Gregory Haskins wrote:
> >>
> >>> In this case the x86 is the owner and the ppc boards use translated
> >>> access. Just switch drivers and device and it falls into place.
> >>>
> >>>
> >> You could switch vbus roles as well, I suppose.
> >
> > Right, there's not real difference in this regard.
> >
> >> Another potential
> >> option is that he can stop mapping host memory on the guest so that it
> >> follows the more traditional model. As a bus-master device, the ppc
> >> boards should have access to any host memory at least in the GFP_DMA
> >> range, which would include all relevant pointers here.
> >>
> >> I digress: I was primarily addressing the concern that Ira would need
> >> to manage the "host" side of the link using hvas mapped from userspace
> >> (even if host side is the ppc boards). vbus abstracts that access so as
> >> to allow something other than userspace/hva mappings. OTOH, having each
> >> ppc board run a userspace app to do the mapping on its behalf and feed
> >> it to vhost is probably not a huge deal either. Where vhost might
> >> really fall apart is when any assumptions about pageable memory occur,
> >> if any.
> >>
> >
> > Why? vhost will call get_user_pages() or copy_*_user() which ought to
> > do the right thing.
>
> I was speaking generally, not specifically to Ira's architecture. What
> I mean is that vbus was designed to work without assuming that the
> memory is pageable. There are environments in which the host is not
> capable of mapping hvas/*page, but the memctx->copy_to/copy_from
> paradigm could still work (think rdma, for instance).
rdma interfaces are typically asynchronous, so blocking
copy_from/copy_to can be made to work, but likely won't work
that well. DMA might work better if it is asynchronous as well.
Assuming a synchronous copy is what we need - maybe the issue is that
there aren't good APIs for x86/ppc communication? If so, sticking them in
vhost might not be the best place. Maybe the specific platform can
redefine copy_to/from_user to do the right thing? Or, maybe add another
API for that ...
> >
> >> As an aside: a bigger issue is that, iiuc, Ira wants more than a single
> >> ethernet channel in his design (multiple ethernets, consoles, etc). A
> >> vhost solution in this environment is incomplete.
> >>
> >
> > Why? Instantiate as many vhost-nets as needed.
>
> a) what about non-ethernets?
vhost-net actually does not care.
the packet is passed on to a socket, we are done.
> b) what do you suppose this protocol to aggregate the connections would
> look like? (hint: this is what a vbus-connector does).
You are talking about management protocol between ppc and x86, right?
One wonders why does it have to be in kernel at all.
> c) how do you manage the configuration, especially on a per-board basis?
not sure what a board is, but configuration is done in userspace.
--
MST
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2009-09-15 14:28 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1251388414.git.mst@redhat.com>
2009-08-27 16:06 ` [PATCHv5 1/3] mm: export use_mm/unuse_mm to modules Michael S. Tsirkin
2009-08-28 15:31 ` Gregory Haskins
2009-08-27 16:07 ` [PATCHv5 2/3] mm: reduce atomic use on use_mm fast path Michael S. Tsirkin
2009-08-27 16:07 ` [PATCHv5 3/3] vhost_net: a kernel-level virtio server Michael S. Tsirkin
2009-09-03 18:39 ` Ira W. Snyder
2009-09-07 10:15 ` Michael S. Tsirkin
2009-09-08 17:20 ` Ira W. Snyder
2009-09-08 20:14 ` Michael S. Tsirkin
2009-09-11 15:17 ` Xin, Xiaohui
2009-09-13 5:46 ` Michael S. Tsirkin
2009-09-14 5:57 ` Xin, Xiaohui
2009-09-14 7:05 ` Michael S. Tsirkin
2009-09-11 16:00 ` Gregory Haskins
2009-09-11 16:14 ` Gregory Haskins
2009-09-13 12:01 ` Michael S. Tsirkin
2009-09-14 16:08 ` Gregory Haskins
2009-09-14 16:47 ` Michael S. Tsirkin
2009-09-14 19:14 ` Gregory Haskins
2009-09-15 12:35 ` Avi Kivity
2009-09-15 13:03 ` Gregory Haskins
2009-09-15 13:25 ` Avi Kivity
2009-09-15 13:50 ` Gregory Haskins
2009-09-15 14:28 ` Michael S. Tsirkin [this message]
2009-09-15 15:03 ` Avi Kivity
2009-09-15 20:08 ` Gregory Haskins
2009-09-15 20:40 ` Michael S. Tsirkin
2009-09-15 20:43 ` Gregory Haskins
2009-09-15 21:25 ` Michael S. Tsirkin
2009-09-15 21:39 ` Gregory Haskins
2009-09-15 21:38 ` Michael S. Tsirkin
2009-09-15 21:55 ` Gregory Haskins
2009-09-16 14:57 ` Arnd Bergmann
2009-09-16 15:13 ` Michael S. Tsirkin
2009-09-16 15:22 ` Arnd Bergmann
2009-09-16 16:08 ` Michael S. Tsirkin
2009-09-16 8:23 ` Avi Kivity
2009-09-16 11:44 ` Gregory Haskins
2009-09-16 13:05 ` Avi Kivity
2009-09-16 14:10 ` Gregory Haskins
2009-09-16 15:59 ` Avi Kivity
2009-09-16 19:22 ` Gregory Haskins
2009-09-16 21:00 ` Avi Kivity
2009-09-17 3:11 ` Gregory Haskins
2009-09-17 7:49 ` Avi Kivity
2009-09-17 14:16 ` Javier Guerra
2009-09-21 21:43 ` Ira W. Snyder
2009-09-22 9:43 ` Avi Kivity
2009-09-22 15:25 ` Ira W. Snyder
2009-09-22 15:56 ` Avi Kivity
2009-09-23 14:26 ` Gregory Haskins
2009-09-23 14:37 ` Avi Kivity
2009-09-23 15:10 ` Gregory Haskins
2009-09-23 17:58 ` Gregory Haskins
2009-09-23 19:37 ` Avi Kivity
2009-09-23 21:15 ` Gregory Haskins
2009-09-24 7:18 ` Avi Kivity
2009-09-24 18:03 ` Gregory Haskins
2009-09-25 8:22 ` Avi Kivity
2009-09-25 21:32 ` Gregory Haskins
2009-09-27 9:43 ` Avi Kivity
2009-09-30 20:04 ` Gregory Haskins
2009-10-01 8:34 ` Avi Kivity
2009-10-01 9:28 ` Michael S. Tsirkin
2009-10-01 19:24 ` Gregory Haskins
2009-10-03 10:00 ` Avi Kivity
2009-09-24 19:27 ` Ira W. Snyder
2009-09-25 7:43 ` Avi Kivity
2009-09-24 8:03 ` Avi Kivity
2009-09-24 18:04 ` Gregory Haskins
2009-09-17 3:57 ` Michael S. Tsirkin
2009-09-17 4:13 ` Gregory Haskins
2009-09-15 12:32 ` Avi Kivity
2009-09-14 16:53 ` Michael S. Tsirkin
2009-09-14 19:28 ` Gregory Haskins
2009-09-25 17:01 ` Ira W. Snyder
2009-09-27 7:43 ` Michael S. Tsirkin
[not found] <E88DD564E9DC5446A76B2B47C3BCCA150219600F9B@pdsmsx503.ccr.corp.intel.com>
2009-08-31 11:42 ` Xin, Xiaohui
2009-08-31 15:23 ` Arnd Bergmann
2009-09-01 14:58 ` Xin, Xiaohui
2009-08-31 17:52 ` Avi Kivity
2009-08-31 21:56 ` Anthony Liguori
2009-09-01 15:37 ` Xin, Xiaohui
2009-09-01 5:04 ` Xin, Xiaohui
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=20090915142821.GA24488@redhat.com \
--to=mst@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=alacrityvm-devel@lists.sourceforge.net \
--cc=avi@redhat.com \
--cc=gregory.haskins@gmail.com \
--cc=hpa@zytor.com \
--cc=iws@ovro.caltech.edu \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@elte.hu \
--cc=netdev@vger.kernel.org \
--cc=rusty@rustcorp.com.au \
--cc=s.hetze@linux-ag.com \
--cc=virtualization@lists.linux-foundation.org \
/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).