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Subject: Re: [virtio-dev] [PATCH v3] pci: new configuration layout
"Michael S. Tsirkin" <firstname.lastname@example.org> writes: > On Thu, Sep 19, 2013 at 11:53:24AM +0930, Rusty Russell wrote: >> We should also define what "locks in" feature negotiation: that was >> simple for single 32-bit field. Should we define this in a >> transport-independent way, or leave it to the transports? >> >> We could overload the DRIVER status bit (which Linux currently calls too >> early, though moving it would be harmless), or add a new one. > > I'm surprised. > I always read 2.2.1. Device Initialization as > an explicit requirement that DRIVER_OK locks the features, > and that's in a transport-independent section and > works for existing guests. > > And if that's not explicit enough, would the proposed > resolution for VIRTIO-30 make it explicit enough? Linux violates this, as it makes the device live *then* sets DRIVER_OK. This means we can use the device (and *do*, for virtio_blk partition scanning) before finalizing features. We could become compliant by setting DRIVER_OK before calling the driver, but that's be misleading: we'd not expect DRIVER_OK if the driver init failed. So I think we will need a new bit, FEATURES_OK? Cheers, Rusty.