Re: [Xen-devel] [PATCH RFC] stubdom: Change vTPM shared page ABI

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-11-28 at 22:22 +0000, Matthew Fioravante wrote:
> On 11/28/2012 03:46 PM, Konrad Rzeszutek Wilk wrote:

> > We could cop out and just name this new driver differently. Then
> > we would not have to deal with the older ones.
> I've already done that with my patch on the linux mailing list. The old 
> frontend driver name was tpm_xenu.ko, the new one is xen-tpmfront.ko.

The name of the driver module isn't really relevant here, what matters
is the name component of the xenstore paths used to trigger the creation
the front and back devices, if they end up loading mutually
incomprehensible versions of front and back then I expect that the
failure case will be pretty hard to diagnose.

The code I'm talking about is a handful of lines in both front and back,
with $OTHEREND substituted as appropriate:

        err = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
        if (err) {
                message = "writing feature-protocol-v2";
                goto abort_transaction;
        }
        ...
        if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-protocol-v2", "%d", 
&val) < 0) {
                printk(KERN_WARN "Warning: $OTHEREND does not appear to support 
feature-protocol-v2\n");
                printk(KERN_WARN "Perhaps it is running the obsolete out of 
tree vtpm driver?\n");
                return -EFOOBAR;
        }

Tweak the actual wording to taste.

If there is a better/more descriptive name for the new protocol than
"protocol-v2" that would be better, or you could put the 2 into the
value (e.g. protocol = 2) and check via that instead (a bit more future
proof perhaps?).

Ian.


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