Messages in this thread | | | Subject | Re: [tpmdd-devel] [PATCH 2/2] tpm2-space: add handling for global session exhaustion | From | James Bottomley <> | Date | Tue, 31 Jan 2017 15:24:44 -0800 |
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On Mon, 2017-01-30 at 00:02 +0200, Jarkko Sakkinen wrote: > On Fri, Jan 27, 2017 at 04:33:54PM -0800, James Bottomley wrote: > > In a TPM2, sessions can be globally exhausted once there are > > TPM_PT_ACTIVE_SESSION_MAX of them (even if they're all context > > saved). > > The Strategy for handling this is to keep a global count of all the > > sessions along with their creation time. Then if we see the TPM > > run > > out of sessions (via the TPM_RC_SESSION_HANDLES) we first wait for > > one > > to become free, but if it doesn't, we forcibly evict an existing > > one. > > The eviction strategy waits until the current command is repeated > > to > > evict the session which should guarantee there is an available > > slot. > > > > On the force eviction case, we make sure that the victim session is > > at > > least SESSION_TIMEOUT old (currently 2 seconds). The wait queue > > for > > session slots is a FIFO one, ensuring that once we run out of > > sessions, everyone will get a session in a bounded time and once > > they > > get one, they'll have SESSION_TIMEOUT to use it before it may be > > subject to eviction. > > > > Signed-off-by: James Bottomley < > > James.Bottomley@HansenPartnership.com> > > --- > > drivers/char/tpm/tpm-chip.c | 1 + > > drivers/char/tpm/tpm.h | 39 +++++++- > > drivers/char/tpm/tpm2-cmd.c | 15 +++ > > drivers/char/tpm/tpm2-space.c | 209 > > ++++++++++++++++++++++++++++++++++++++++-- > > drivers/char/tpm/tpms-dev.c | 17 +++- > > 5 files changed, 271 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm > > -chip.c > > index 6282ad0..150c6b8 100644 > > --- a/drivers/char/tpm/tpm-chip.c > > +++ b/drivers/char/tpm/tpm-chip.c > > @@ -164,6 +164,7 @@ struct tpm_chip *tpm_chip_alloc(struct device > > *pdev, > > > > mutex_init(&chip->tpm_mutex); > > init_rwsem(&chip->ops_sem); > > + init_waitqueue_head(&chip->session_wait); > > > > chip->ops = ops; > > > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h > > index 10c57b9..658e5e2 100644 > > --- a/drivers/char/tpm/tpm.h > > +++ b/drivers/char/tpm/tpm.h > > @@ -95,7 +95,8 @@ enum tpm2_return_codes { > > TPM2_RC_HANDLE = 0x008B, > > TPM2_RC_INITIALIZE = 0x0100, /* RC_VER1 */ > > TPM2_RC_DISABLED = 0x0120, > > - TPM2_RC_TESTING = 0x090A, /* RC_WARN */ > > + TPM2_RC_SESSION_HANDLES = 0x0905, /* RC_WARN */ > > + TPM2_RC_TESTING = 0x090A, > > TPM2_RC_REFERENCE_H0 = 0x0910, > > }; > > > > @@ -139,7 +140,8 @@ enum tpm2_capabilities { > > }; > > > > enum tpm2_properties { > > - TPM_PT_TOTAL_COMMANDS = 0x0129, > > + TPM_PT_TOTAL_COMMANDS = 0x0129, > > + TPM_PT_ACTIVE_SESSIONS_MAX = 0x0111, > > }; > > > > enum tpm2_startup_types { > > @@ -163,8 +165,24 @@ struct tpm_space { > > u8 *context_buf; > > u32 session_tbl[3]; > > u8 *session_buf; > > + u32 reserved_handle; > > }; > > > > +#define TPM2_HANDLE_FORCE_EVICT 0xFFFFFFFF > > + > > +static inline void tpm2_session_force_evict(struct tpm_space > > *space) > > +{ > > + /* if reserved handle is not empty, we already have a > > + * session for eviction, so no need to force one > > + */ > > + if (space->reserved_handle == 0) > > + space->reserved_handle = TPM2_HANDLE_FORCE_EVICT; > > +} > > +static inline bool tpm2_is_session_force_evict(struct tpm_space > > *space) > > +{ > > + return space->reserved_handle == TPM2_HANDLE_FORCE_EVICT; > > +} > > + > > enum tpm_chip_flags { > > TPM_CHIP_FLAG_TPM2 = BIT(1), > > TPM_CHIP_FLAG_IRQ = BIT(2), > > @@ -177,6 +195,12 @@ struct tpm_chip_seqops { > > const struct seq_operations *seqops; > > }; > > > > +struct tpm_sessions { > > + struct tpm_space *space; > > + u32 handle; > > + unsigned long created; > > +}; > > I would rethink this a bit. I kind of dislike this structure as it > > I would rather have > > struct tpm_session { > u32 handle; > unsigned long created; > }; > > and in struct tpm_space: > > struct tpm_session session_tbl[3]; > struct list_head session_list; > > and keep those instances that have sessions in that linked list. > > What do you think?
I can do ... but tpm_session will also need a struct list_head node so it can be placed on the list ...
If I'm listifying, I'd probably also add a hash bucket list for easy lookup by session.
James
> I'll study the actual functionality in this patch properly later. > > /Jarkko > > --------------------------------------------------------------------- > --------- > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > _______________________________________________ > tpmdd-devel mailing list > tpmdd-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/tpmdd-devel >
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