linux-kernel - Re: [PATCH v3] drivers/tpm: add xen tpmfront interface

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Message-ID: <51A51782.2070406@tycho.nsa.gov>
Date:	Tue, 28 May 2013 16:45:54 -0400
From:	Daniel De Graaf <dgdegra@...ho.nsa.gov>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	linux-kernel@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net,
	xen-devel@...ts.xen.org, mail@...jiv.net, tpmdd@...horst.net,
	tpmdd@...rix.com, leosilva@...ux.vnet.ibm.com,
	adlai@...ux.vnet.ibm.com, shpedoikal@...il.com
Subject: Re: [PATCH v3] drivers/tpm: add xen tpmfront interface

On 05/28/2013 04:32 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, May 28, 2013 at 11:40:32AM -0400, Daniel De Graaf wrote:
>> This is a complete rewrite of the Xen TPM frontend driver, taking
>> advantage of a simplified frontend/backend interface and adding support
>> for cancellation and timeouts.  The backend for this driver is provided
>> by a vTPM stub domain using the interface in Xen 4.3.
>>
>> Signed-off-by: Daniel De Graaf <dgdegra@...ho.nsa.gov>
>> Acked-by: Matthew Fioravante <matthew.fioravante@...apl.edu>
>
> .. snip..
>> +static void ring_free(struct tpm_private *priv)
>> +{
>> +	if (!priv)
>> +		return;
>> +
>> +	if (priv->ring_ref)
>> +		gnttab_end_foreign_access(priv->ring_ref, 0,
>> +				(unsigned long)priv->shr);
>> +	else
>> +		free_page((unsigned long)priv->shr);
>> +
>> +	if (priv->chip && priv->chip->vendor.irq)
>> +		unbind_from_irqhandler(priv->chip->vendor.irq, priv);
>
> You are missing:
>
> 	if (priv->evtchn != INVALID_EVTCHN)
> 		xenbus_free_evtchn(priv->xdev, priv->evtchn);

This is already handled by unbind_from_irqhandler when it calls
unbind_from_irq, which gets the event channel from the IRQ. This
should be the same event channel as priv->evtchn, and it already
calls EVTCHNOP_close on this port. Calling xenbus_free_evtchn on
the event channel again will just double-free the port.

This is done the same way as drivers/block/xen-blkfront.c, for
reference.

>> +
>> +	kfree(priv);
>> +}
>> +


-- 
Daniel De Graaf
National Security Agency
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