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Subject[PATCH 4.4 045/160] tpm: Restore functionality to xen vtpm driver.
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Dr. Greg Wettstein <>

commit e487a0f52301293152a6f8c4e217f2a11dd808e3 upstream.

Functionality of the xen-tpmfront driver was lost secondary to
the introduction of xenbus multi-page support in commit ccc9d90a9a8b
("xenbus_client: Extend interface to support multi-page ring").

In this commit pointer to location of where the shared page address
is stored 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

<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.

Fixes: ccc9d90a9a8b ("xenbus_client: Extend interface to support multi-page ring")
Signed-off-by: Dr. Greg Wettstein <>
Signed-off-by: Greg Kroah-Hartman <>

[boris: Updated commit message, added Fixes tag]
Signed-off-by: Boris Ostrovsky <>
Cc: # v4.1+
Reviewed-by: Jarkko Sakkinen <>
Signed-off-by: Jarkko Sakkinen <>

drivers/char/tpm/xen-tpmfront.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -201,7 +201,7 @@ static int setup_ring(struct xenbus_devi
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;

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