Re: [virtio-dev] [PATCH 1/1] Allow "Vendor Specific" extension to virtio PCI capabilities.

[Stefan Hajnoczi <stefanha@redhat.com>]

On Thu, May 17, 2018 at 09:06:04AM -0400, Venu Busireddy wrote:

Can you describe a use case where vendor-specific extensions make sense
as opposed to extending the VIRTIO specification?

This proposal only supports the PCI transport, so do extensions only
affect the PCI transport behavior or also other aspects of VIRTIO
(device behavior, vring, etc)?

> +\devicenormative{\paragraph}{Vendor Specific Extension capability}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Vendor Specific Extension capability}
> +
> +The device may or may not present the VIRTIO_PCI_CAP_VENDOR_EXT_CFG capability.

s/may or may not/MAY/

> +
> +\drivernormative{\paragraph}{Vendor Specific Extension capability}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Vendor Specific Extension capability}
> +
> +The driver MUST NOT write to vendor_specific_data[] area or the BAR region.

How does a driver identify vendor-specific extensions that it supports?
No Vendor ID is included in the capability, just an opaque blob, so how
are collisions avoided?

How does a driver behave upon encountering an unknown vendor-specific
extension?

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