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From: Logan Gunthorpe <logang@deltatee.com>
To: Vincent Whitchurch <vincent.whitchurch@axis.com>,
	Arnd Bergmann <arnd@arndb.de>
Cc: sudeep.dutt@intel.com, ashutosh.dixit@intel.com,
	gregkh <gregkh@linuxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-pci <linux-pci@vger.kernel.org>,
	linux-ntb@googlegroups.com, Jon Mason <jdmason@kudzu.us>,
	Dave Jiang <dave.jiang@intel.com>,
	Allen Hubbe <allenbh@gmail.com>
Subject: Re: [PATCH 0/8] Virtio-over-PCIe on non-MIC
Date: Thu, 17 Jan 2019 15:17:41 -0700	[thread overview]
Message-ID: <62e5f3e7-e2e3-c6ce-b8f6-99a5342c1494@deltatee.com> (raw)
In-Reply-To: <20190117151906.odvozs6kz3uvx32y@axis.com>



On 2019-01-17 8:19 a.m., Vincent Whitchurch wrote:
> On the endpoint, the PCIe endpoint driver sets up (hardcoded) BARs and
> memory regions as required to allow the endpoint and the root complex to
> access each other's memory.

This statement describes NTB hardware pretty well. In essence that's
what an NTB device is: a BAR that maps to a window in other hosts memory.

Right now the entire NTB upstream software stack (ntb_transport and
ntb_netdev) is specific to that ecosystem and only exposes a network
device so the hosts can communicate. This code works but has some issues
and was never able to perform at full PCIe line speeds (which everyone
expects). So it's not clear to me if anyone is doing anything real with
it. The companies that are working on NTB, that I'm aware of, have
mostly done their own out-of-tree stuff.

It would be interesting to unify ntb_transport with the virtio stack
because I suspect they do very similar things right now and there's a
lot more devices above virtio than just a network device. However, the
main problem people working on NTB face (besides performance) is trying
to get multi-host working in a general and sensible way given that the
hardware typically has limited BAR resources (among other limitations).

Logan

  parent reply	other threads:[~2019-01-17 22:18 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 16:32 [PATCH 0/8] Virtio-over-PCIe on non-MIC Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 1/8] vop: Use %z for size_t Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 2/8] vop: Cast pointers to uintptr_t Vincent Whitchurch
2019-01-16 17:39   ` Joe Perches
2019-01-22 10:41   ` Greg KH
2019-01-16 16:32 ` [PATCH 3/8] vop: Add definition of readq/writeq if missing Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 4/8] vop: Allow building on more systems Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 5/8] vop: vringh: Do not crash if no DMA channel Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 6/8] vop: Fix handling of >32 feature bits Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 7/8] vop: Use consistent DMA Vincent Whitchurch
2019-01-16 16:32 ` [PATCH 8/8] vop: Add loopback Vincent Whitchurch
2019-01-16 17:07 ` [PATCH 0/8] Virtio-over-PCIe on non-MIC Arnd Bergmann
2019-01-17 10:54   ` Vincent Whitchurch
2019-01-17 12:39     ` Arnd Bergmann
2019-01-17 15:15       ` Christoph Hellwig
2019-01-17 15:19         ` Christoph Hellwig
2019-01-17 15:31           ` Arnd Bergmann
2019-01-17 15:19       ` Vincent Whitchurch
2019-01-17 15:21         ` Christoph Hellwig
2019-01-17 15:32           ` Vincent Whitchurch
2019-01-17 15:46             ` Christoph Hellwig
2019-01-17 16:18               ` Arnd Bergmann
2019-01-17 15:53         ` Arnd Bergmann
2019-01-17 16:26           ` Vincent Whitchurch
2019-01-17 16:34             ` Arnd Bergmann
2019-01-17 22:17         ` Logan Gunthorpe [this message]
2019-01-18 23:49 ` Stephen Warren
2019-01-21 16:25   ` Vincent Whitchurch
2019-01-22 10:45 ` Greg KH

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