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.bottom...@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'll study the actual functionality in this patch properly later. /Jarkko