On 10/01/2015 02:31 PM, Michael S. Tsirkin wrote: > 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. >
Ok. So yes, the tx ring can be mapped R/W.
