From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: Having troubles binding an SR-IOV VF to
 uio_pci_generic on Amazon instance
Date: Thu, 1 Oct 2015 14:31:35 +0300
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To: Avi Kivity <avi@scylladb.com>
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On Thu, Oct 01, 2015 at 02:20:37PM +0300, Avi Kivity wrote:
> 
> 
> On 10/01/2015 02:09 PM, Michael S. Tsirkin wrote:
> >On Thu, Oct 01, 2015 at 01:50:10PM +0300, Avi Kivity wrote:
> >>>>It's not just the lack of system calls, of course, the architecture is
> >>>>completely different.
> >>>Absolutely - I'm not saying move all of DPDK into kernel.
> >>>We just need to protect the RX rings so hardware does
> >>>not corrupt kernel memory.
> >>>
> >>>
> >>>Thinking about it some more, many devices
> >>>have separate rings for DMA: TX (device reads memory)
> >>>and RX (device writes memory).
> >>>With such devices, a mode where userspace can write TX ring
> >>>but not RX ring might make sense.
> >>I'm sure you can cause havoc just by reading, if you read from I/O memory.
> >Not talking about I/O memory here. These are device rings in RAM.
> 
> Right.  But you program them with DMA addresses, so the device can read
> another device's memory.

It can't if host has limited it to only DMA into guest RAM, which is
pretty common.

-- 
MST