linux-kernel - Re: [PATCH] tpm: Restore functionality to xen vtpm driver.

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Date:   Fri, 20 Jan 2017 17:22:25 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     greg@...ellic.com, linux-kernel@...r.kernel.org
Cc:     dgdegra@...ho.nsa.gov, konrad.wilk@...cle.com,
        jarkko.sakkinen@...ux.intel.com
Subject: Re: [PATCH] tpm: Restore functionality to xen vtpm driver.

On 01/20/2017 10:00 AM, Dr. Greg Wettstein wrote:
> 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@...r.kernel.org> # 4.1-

4.1+, I believe.

> Suggested-by: Daniel De Graaf <dgdegra@...ho.nsa.gov>
> Signed-off-by: Dr. Greg Wettstein <greg@...ellic.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>

> ---
>  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;
>