[PATCH] tpm: Restore functionality to xen vtpm driver.

[Dr. Greg Wettstein]

Functionality of the xen-tpmfront driver was lost secondary to
the introduction of xenbus multi-page support in the following
commit:

ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d

xenbus_client: Extend interface to support multi-page ring

In this commit a pointer to the shared page address was being
passed to the xenbus_grant_ring() function rather then the
address of the shared page itself.  This resulted in a situation
where the driver would attach to the vtpm-stubdom but any attempt
to send a command to the stub domain would timeout.

A diagnostic finding for this regression is the following error
message being generated when the xen-tpmfront driver probes for a
device:

<3>vtpm vtpm-0: tpm_transmit: tpm_send: error -62

<3>vtpm vtpm-0: A TPM error (-62) occurred attempting to determine the timeouts

This fix is relevant to all kernels from 4.1 forward which is the
release in which multi-page xenbus support was introduced.

Daniel De Graaf formulated the fix by code inspection after the
regression point was located.

Cc: <stable@xxxxxxxxxxxxxxx> # 4.1-
Suggested-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Signed-off-by: Dr. Greg Wettstein <greg@xxxxxxxxxxxx>
---
 drivers/char/tpm/xen-tpmfront.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
index 3111f2778079..d1478f7b3f97 100644
--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -201,7 +201,7 @@ static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
 		return -ENOMEM;
 	}
 
-	rv = xenbus_grant_ring(dev, &priv->shr, 1, &gref);
+	rv = xenbus_grant_ring(dev, priv->shr, 1, &gref);
 	if (rv < 0)
 		return rv;
 
-- 
2.11.0

As always,
Dr. G.W. Wettstein, Ph.D.   Enjellic Systems Development, LLC.
4206 N. 19th Ave.           Specializing in information infra-structure
Fargo, ND  58102            development.
PH: 701-281-1686
FAX: 701-281-3949           EMAIL: greg@xxxxxxxxxxxx
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"I will not eat aged beef."
                                -- Johannes Christian Grosen
                                   Resurrection.

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