Re: [virtio-comment] [PATCH 1/1] content: Reserve virtio-nsm device ID

[Stefan Hajnoczi <stefanha@redhat.com>]

On Thu, May 21, 2020 at 01:49:42PM +0300, Petre Eftime wrote:
> The NitroSecureModule is a device with a very stripped down
> Trusted Platform Module functionality, which is used in the
> context of a Nitro Enclave (see https://lkml.org/lkml/2020/4/21/1020)
> to provide boot time measurement and attestation.
> 
> Since this device provides some critical cryptographic operations,
> there are a series of operations which are required to have guarantees
> of atomicity, ordering and consistency: operations fully succeed or fully
> fail, including when some external events might interfere in the
> process: live migration, crashes, etc; any failure in the critical
> section requires termination of the enclave it is attached to, so
> the device needs to be as resilient as possible, simplicity is
> strongly desired.
> 
> To account for that, the device and driver are made to have very few
> error cases in the critical path and the operations themselves can be
> rolled back and retried if events happen outside the critical
> area, while processing a request. The driver itself can be made very
> simple and thus is easily portable.
> 
> Since the requests can be handled directly in the virtio queue, serving
> most requests requires no additional buffering or memory allocations
> on the host side.
> 
> Signed-off-by: Petre Eftime <epetre@amazon.com>
> ---
>  content.tex | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/content.tex b/content.tex
> index 91735e3..6eee371 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -2801,6 +2801,8 @@ \chapter{Device Types}\label{sec:Device Types}
>  \hline
>  31         &   Video decoder device \\
>  \hline
> +0xec2000   &   NitroSecureModule \\

The PCI and CCW transports represent VIRTIO device type IDs with 16-bit
fields. Is there a reason why the NitroSecureModule device should only
work with VIRTIO transports that support >16-bit device type IDs?

If not, then please pick the next low-numbered ID instead.

Stefan

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