netdev - Re: [RFC v2] virtio: add virtio-over-PCI driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <49E50DC4.3080108@ovro.caltech.edu>
Date:	Tue, 14 Apr 2009 15:27:16 -0700
From:	David Hawkins <dwh@...o.caltech.edu>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	Ira Snyder <iws@...o.caltech.edu>, Arnd Bergmann <arnd@...db.de>,
	Jan-Bernd Themann <THEMANN@...ibm.com>, netdev@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [RFC v2] virtio: add virtio-over-PCI driver

Hi Grant,

> Hmmm, I hadn't thought about this.  I was intending to use the
> Virtex's memory region for all virtio, but if I can allocate memory
> regions on both sides of the PCI bus, then that may be best.

Sounds like you can experiment and see what works best :)

>> If you use
>> a PCI Target only core, then the MPC5200 DMA controller
>> will have to do all the work, and read transfers might
>> be slightly less efficient.
> 
> I'll definitely intend to enable master mode on the Xilinx PCI controller.

Since you understand the lingo, you clearly understand
there are core differences :)

>> Our target boards (PowerPC) live in compactPCI backplanes
>> and talk to x86 boards that do not have DMA controllers.
>> So the PCI target board DMA controllers are used to
>> transfer data efficiently to the x86 host (writes)
>> and less efficiently from the host to the boards
>> (reads). Our bandwidth requirements are 'to the host',
>> so we can live with the asymmetry in performance.
> 
> Fortunately I don't have very high bandwidth requirements for the
> first spin, so I have some room to experiment.  :-)

Yes, in theory you have enough bandwidth ... then a
few features are added, the PCI core is not quite as
fast as advertised, etc etc :)

Cheers,
Dave
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html