Re: [Xen-devel] [PATCH v5.1 01/12] mini-os/tpm{back, front}: Change shared page ABI

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-03-22 at 22:30 +0000, Daniel De Graaf wrote:
> 
> +struct vtpm_shared_page {
> +    uint32_t length;         /* request/response length in bytes */

The data is inline immediately after this struct? How does it interact
with the extra_pages stuff?

> +
> +    uint8_t state;           /* enum vtpm_state */
> +    uint8_t locality;        /* for the current request */

I've had a look at the 7/12 and 10/12 and I'm still not sure how this
byte is used -- it's looked up in the XSM label as a string but how does
it become a uint8_t agreed by both the front and backend?

Could we perhaps get a few more words on the protocol in general? Or
have I missed some existing doc?

What is the format of the payload, is it defined by some independent TPM
standard?

> +    uint8_t pad;             /* should be zero */
> +
> +    uint8_t nr_extra_pages;  /* extra pages for long packets; may be zero */
> +    uint32_t extra_pages[0]; /* grant IDs; length is actually nr_extra_pages 
> */

Not actually used AFAICT? Future expansion I presume?

> +};
> +typedef struct vtpm_shared_page vtpm_shared_page_t; 


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