From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43979) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TwM5i-0002sb-58 for qemu-devel@nongnu.org; Fri, 18 Jan 2013 19:15:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TwM5g-0000HK-OD for qemu-devel@nongnu.org; Fri, 18 Jan 2013 19:15:21 -0500 Received: from e9.ny.us.ibm.com ([32.97.182.139]:40807) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TwM5g-0008Tm-LP for qemu-devel@nongnu.org; Fri, 18 Jan 2013 19:15:20 -0500 Received: from /spool/local by e9.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 18 Jan 2013 19:15:02 -0500 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 816B538C8046 for ; Fri, 18 Jan 2013 19:14:59 -0500 (EST) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r0J0Ewf2333416 for ; Fri, 18 Jan 2013 19:14:59 -0500 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r0J0Ew9J020477 for ; Fri, 18 Jan 2013 17:14:58 -0700 Message-ID: <50F9E580.2000602@linux.vnet.ibm.com> Date: Fri, 18 Jan 2013 19:14:56 -0500 From: Stefan Berger MIME-Version: 1.0 References: <1358524968-22297-1-git-send-email-stefanb@linux.vnet.ibm.com> <1358524968-22297-9-git-send-email-stefanb@linux.vnet.ibm.com> <50F991FE.3000901@redhat.com> In-Reply-To: <50F991FE.3000901@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V20 8/8] Add fd parameter for TPM passthrough driver List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: mst@redhat.com, qemu-devel@nongnu.org, anthony@codemonkey.ws, andreas.niederl@iaik.tugraz.at On 01/18/2013 01:18 PM, Eric Blake wrote: > On 01/18/2013 09:02 AM, Stefan Berger wrote: >> Enable the passing of a file descriptor via fd=<..> to access the host's >> TPM device using the TPM passthrough driver. > Do we still need this, or is it sufficient to use path=/dev/fdset/nnn, > so that we are reusing common fd passing mechanisms without inventing > yet more variants? Well, it's similar to -netdev tap,fd=27,id=xyz > >> +++ b/qapi-schema.json >> @@ -3033,11 +3033,13 @@ >> # >> # @cancel_path: #optional Path to TPM backend device's cancel sysfs entry >> # >> +# @fd: #optional File descriptor for the TPM backend device >> +# >> # Since: 1.5.0 >> ## >> { 'type': 'TPMInfo', >> 'data': {'model': 'str', 'id': 'str', 'type': 'str', '*path': 'str', >> - '*cancel_path': 'str' } } >> + '*cancel_path': 'str', '*fd' : 'int' } } > Besides, what integer value would you use for fd? Older commands that > support fd passing did so via 'int' on the command line, but via a 'str' > via QMP (the name associated with the fd when using 'getfd'), since QMP > does not have a way to expose _which_ fd is the right number from qemu's When libvirt forks, the child process inherits the file descriptors, among them those of the taps and /dev/tpm0. The subsequent execve keeps the file descriptor open. QEMU then reads the TPM file descriptor from the command line into above TPMInfo->fd. This also works with 'exec 100<>/dev/tpm0' via command line. Similar to the SELinux labeling of all the other file descriptors I also use the one for the TPM device for SELinux labeling. > perspective (it's not necessarily the same fd as in the management process). Hm. > I think this patch should just be dropped. > Regards, Stefan