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Subject: Re: [virtio] Groups - Action Item "Create text version of virtio 0.9.5 document" added
On Wed, 2013-07-31 at 15:51 +0100, Anthony Liguori wrote: > > On Wed, 2013-07-31 at 14:25 +0100, Anthony Liguori wrote: > >> I'm not sure where this discussion took place, but there is nothing in > >> QEMU that requires a dummy device to be used. > > > > http://thread.gmane.org/gmane.linux.kernel.virtualization/20144 > > N.B. If you aren't discussing something on qemu-devel, then you aren't > getting the full input of the community. The discussion was more about virtio, not qemu. Nevertheless I blame Peter :-) > > It is very unsafe to "probe" memory mapped peripherals. > It simply depends on the devices. It depends on the architecture and interconnect more than on the device. I'm not talking about potential dangerous side effects of reading a device's register. I'm talking about generating a read transaction on a address not known to the interconnect or - even worse - belonging to a powered-down device. In such cases you can *completely* lock down the system. It's not really relevant here - let's just agree that blind reads are unsafe. > > Maybe instead of > > defining zero as a do-nothing-device we should simply make this value > > reserved or illegal? > > Yes, I think that's a good idea. > > > This would make PCI situation clear (no device will > > be ever allowed to have it) and mmio driver could "overload" its meaning > > as "ignore". > > Agreed. Cool, I'll proceed in this direction then and once we have a base to work on will submit a patch adding the relevant position to the IDs list. Then we can argue on the value and naming again :-) Paweł
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