On Mon, Apr 10, 2023 at 6:06 PM Michael S. Tsirkin <[email protected]> wrote: > > On Mon, Apr 10, 2023 at 03:20:52PM +0800, Jason Wang wrote: > > On Mon, Apr 10, 2023 at 2:40 PM Michael S. Tsirkin <[email protected]> wrote: > > > > > > On Mon, Apr 10, 2023 at 02:20:16PM +0800, Jason Wang wrote: > > > > On Mon, Apr 10, 2023 at 2:15 PM Michael S. Tsirkin <[email protected]> > > > > wrote: > > > > > > > > > > On Mon, Apr 10, 2023 at 09:33:32AM +0800, Jason Wang wrote: > > > > > > This is fine for vDPA but not for virtio if the design can only work > > > > > > for some specific setups (OSes/archs). > > > > > > > > > > > > Thanks > > > > > > > > > > Well virtio legacy has a long history of documenting existing hacks :) > > > > > > > > Exactly, so the legacy behaviour is not (or can't be) defined by the > > > > spec but the codes. > > > > > > I mean driver behaviour derives from the code but we do document it in > > > the spec to help people build devices. > > > > > > > > > > > But yes, VIRTIO_F_ORDER_PLATFORM has to be documented. > > > > > And we have to decide what to do about ACCESS_PLATFORM since > > > > > there's a security problem if device allows not acking it. > > > > > Two options: > > > > > - relax the rules a bit and say device will assume ACCESS_PLATFORM > > > > > is acked anyway > > > > > > > > This will break legacy drivers which assume physical addresses. > > > > > > not that they are not already broken. > > > > I may miss something, the whole point is to allow legacy drivers to > > run otherwise a modern device is sufficient? > > yes and if legacy drivers don't work in a given setup then we > should not worry. > > > > > > > > > - a new flag that is insecure (so useful for sec but useless for > > > > > dpdk) but optional > > > > > > > > This looks like a new "hack" for the legacy hacks. > > > > > > it's not just for legacy. > > > > We have the ACCESS_PLATFORM feature bit, what is the useage for this new > > flag? > > > ACCESS_PLATFORM is also a security boundary. so devices must fail > negotiation if it's not there. this new one won't be. > > > > > > > > > And what about ORDER_PLATFORM, I don't think we can modify legacy > > > > drivers... > > > > > > > > Thanks > > > > > > You play some tricks with shadow VQ I guess. > > > > Do we really want to add a new feature in the virtio spec that can > > only work with the datapath mediation? > > > > Thanks > > As long as a feature is useful and can't be supported otherwise > we are out of options.
Probably not? Is it as simple as relaxing this: "Transitional devices MUST expose the Legacy Interface in I/O space in BAR0." To allow memory space. This works for both software and hardware devices (I had a handy hardware that supports legacy virtio drivers in this way). Thanks > Keeping field practice things out of the > spec helps no one. > > > > > > > -- > > > MST > > > > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
