Re: [PATCH v5 4/5] Initialize TPM and get durations and timeouts

["Stefan Berger" <stefanb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

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Stefan Berger/Watson/IBM@IBMUS wrote on 02/14/2016 01:37:08 AM:

> 
> Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote on 02/12/
> 2016 01:34:15 PM:
> 
> > 
> > On Fri, Feb 12, 2016 at 01:13:39PM -0500, Stefan Berger wrote:
> > >    Stefan Berger/Watson/IBM@IBMUS wrote on 02/11/2016 10:56:47 PM:
> > >    >
> > >    > Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote on 
02/11/
> > >    > 2016 06:56:11 PM:
> > >    >
> > >    >
> > >    > >
> > >    > > On Thu, Feb 11, 2016 at 05:26:24PM -0500, Stefan Berger 
wrote:
> > >    > >
> > >    > > >    > What is the point of tpmm_chip_dev?
> > >    > > >    So that the usage model of the chip is the same. We get 
this
> > >    in the
> > >    > > >    tpm-vtpm.c with tpm_alloc_chip + tpmm_chip_dev while all
> > >    others can
> > >    > > >    call tpmm_chip_alloc, which combines the two.
> > >    > >
> > >    > > No need, just don't use devm in vtpm, that is even better. 
The
> > >    > > standard devm idiom is a with and without version.
> > >    >
> > >    > Updated the branch. Are you going to upstream your patch? 
Otherwise
> > >    > I would just add your Signed-off-by to it if that's ok ?
> > >    >
> > >    > [1]https://github.com/stefanberger/linux/tree/vtpm-driver.v3
> > >    I converted tpm-chip.c to use IDA as well.
> > >    A test for 4096 vTPM instances:
> > >    for ((i = 0; i < 4096; i++)); do ./vtpmctrl & done
> > 
> > Yeah, that looks good, thanks for doing this
> > 
> 
> With the IDR I ran into the problem that TPM core driver and backend
> now share the ID and create their device names with it. What can 
> happen is that the core driver gives up ID 123, while the vTPM 
> driver still has the device name vtpms123 registered with sysfs. Now
> the next device is created, ID 123 is recycled by the core driver, 
> and it bombs while the vTPM driver again tries to register vtpm123 
> that still hasn't been unregistered. One can trigger this problem 
> with lots of concurrency (see below) and then the whole system even 
> locks up. I don't know how to solve this ID issue in an easier way 
> than having an IDR in the core driver and an IDA in the vTPM driver 
> and so handling the IDs independently. This in turn makes the split 
> of tpmm_chip_alloc / tpm_chip_alloc unnecessary since we don't need 
> the ID from the chip anymore. Now the below test runs stable.

Scratch that. The easier way to fix this was to release the tpm_chip after 
the vtpm_dev.

   Stefan


> 
> 
> for pid in $(ps aux | grep vtpm | gawk '{print $2}'); do kill -9 
> $pid; done ; for ((i =0; i< 8192; i++)); do ./vtpmctrl &>/dev/null & 
done
> 
>  Stefan
> 
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