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

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Message-ID: <20180913202021.GD31953@ziepe.ca>
Date:   Thu, 13 Sep 2018 14:20:21 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     peterhuewe@....de, jarkko.sakkinen@...ux.intel.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, jgross@...e.com, dunlapg@...ch.edu,
        "Dr. Greg Wettstein" <greg@...d.enjellic.com>,
        "Dr . Greg Wettstein" <greg@...ellic.com>, stable@...r.kernel.org
Subject: Re: [PATCH RESEND] tpm: Restore functionality to xen vtpm driver.

On Thu, Sep 13, 2018 at 03:47:49PM -0400, Boris Ostrovsky wrote:
> From: "Dr. Greg Wettstein" <greg@...d.enjellic.com>
> 
> 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").

This should be in a Fixes: line..

> 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.
> 
> Signed-off-by: Dr. Greg Wettstein <greg@...ellic.com>
> 
> [boris: fixed commit message formatting]
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: stable@...r.kernel.org # v4.1+
> We've lost this patch a couple of years ago, re-submitting.
> 
> 
>  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 911475d36800..b150f87f38f5 100644
> +++ b/drivers/char/tpm/xen-tpmfront.c
> @@ -264,7 +264,7 @@ 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;
>