Jason Gunthorpe <[email protected]> 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 <[email protected]> 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.
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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