| Message ID | 20240409190847.10869-3-jarkko@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | TPM documentation updates | expand |
On Tue, Apr 09, 2024 at 10:08:47PM +0300, Jarkko Sakkinen wrote: > diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst > new file mode 100644 > index 000000000000..b448ea3db71d > --- /dev/null > +++ b/Documentation/security/tpm/tpm_tis.rst > @@ -0,0 +1,46 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +========================= > +TPM FIFO interface driver > +========================= > + > +TCG PTP Specification defines two interface types: FIFO and CRB. The former is > +based on sequenced read and write operations, and the latter is based on a > +buffer containing the full command or response. > + > +FIFO (First-In-First-Out) interface is used by the tpm_tis_core dependent > +drivers. Originally Linux had only a driver called tpm_tis, which covered > +memory mapped (aka MMIO) interface but it was later on extended to cover other > +physical interfaces supported by the TCG standard. > + > +For legacy compliance the original MMIO driver is called tpm_tis and the Did you mean "For historical reasons above ..."? > +framework for FIFO drivers is named as tpm_tis_core. The postfix "tis" in > +tpm_tis comes from the TPM Interface Specification, which is the hardware > +interface specification for TPM 1.x chips. > + > +Communication is based on a 20 KiB buffer shared by the TPM chip through a > +hardware bus or memory map, depending on the physical wiring. The buffer is > +further split into five equal-size 4 KiB buffers, which provide equivalent > +sets of registers for communication between the CPU and TPM. These > +communication endpoints are called localities in the TCG terminology. > + > +When the kernel wants to send commands to the TPM chip, it first reserves > +locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is > +cleared by the chip when the access is granted. Once it completes its > +communication, the kernel writes the TPM_ACCESS.activeLocality bit. This > +informs the chip that the locality has been relinquished. > + > +Pending localities are served in order by the chip in descending order, one at > +a time: > + > +- Locality 0 has the lowest priority. > +- Locality 5 has the highest priority. > + > +Further information on the purpose and meaning of the localities can be found > +in section 3.2 of the TCG PC Client Platform TPM Profile Specification. > + > +References > +========== > + > +TCG PC Client Platform TPM Profile (PTP) Specification > +https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/ Other than that, Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
On Thu Apr 11, 2024 at 1:50 PM EEST, Bagas Sanjaya wrote: > On Tue, Apr 09, 2024 at 10:08:47PM +0300, Jarkko Sakkinen wrote: > > diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst > > new file mode 100644 > > index 000000000000..b448ea3db71d > > --- /dev/null > > +++ b/Documentation/security/tpm/tpm_tis.rst > > @@ -0,0 +1,46 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > + > > +========================= > > +TPM FIFO interface driver > > +========================= > > + > > +TCG PTP Specification defines two interface types: FIFO and CRB. The former is > > +based on sequenced read and write operations, and the latter is based on a > > +buffer containing the full command or response. > > + > > +FIFO (First-In-First-Out) interface is used by the tpm_tis_core dependent > > +drivers. Originally Linux had only a driver called tpm_tis, which covered > > +memory mapped (aka MMIO) interface but it was later on extended to cover other > > +physical interfaces supported by the TCG standard. > > + > > +For legacy compliance the original MMIO driver is called tpm_tis and the > Did you mean "For historical reasons above ..."? That would be better wording. > > +framework for FIFO drivers is named as tpm_tis_core. The postfix "tis" in > > +tpm_tis comes from the TPM Interface Specification, which is the hardware > > +interface specification for TPM 1.x chips. > > + > > +Communication is based on a 20 KiB buffer shared by the TPM chip through a > > +hardware bus or memory map, depending on the physical wiring. The buffer is > > +further split into five equal-size 4 KiB buffers, which provide equivalent > > +sets of registers for communication between the CPU and TPM. These > > +communication endpoints are called localities in the TCG terminology. > > + > > +When the kernel wants to send commands to the TPM chip, it first reserves > > +locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is > > +cleared by the chip when the access is granted. Once it completes its > > +communication, the kernel writes the TPM_ACCESS.activeLocality bit. This > > +informs the chip that the locality has been relinquished. > > + > > +Pending localities are served in order by the chip in descending order, one at > > +a time: > > + > > +- Locality 0 has the lowest priority. > > +- Locality 5 has the highest priority. > > + > > +Further information on the purpose and meaning of the localities can be found > > +in section 3.2 of the TCG PC Client Platform TPM Profile Specification. > > + > > +References > > +========== > > + > > +TCG PC Client Platform TPM Profile (PTP) Specification > > +https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/ > > Other than that, > > Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com> Thanks! I'll apply this with the fix you proposed. For everyone: this is by no means perfect. The point is to seed something we can build on top of. So I leave it rather lacking stuff than try to document every possible bells and whistle. This can be then improved based on discussions and future patch sets. BR, Jarkko
diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst index fc40e9f23c85..f27a17f60a96 100644 --- a/Documentation/security/tpm/index.rst +++ b/Documentation/security/tpm/index.rst @@ -5,6 +5,7 @@ Trusted Platform Module documentation .. toctree:: tpm_event_log + tpm_tis tpm_vtpm_proxy xen-tpmfront tpm_ftpm_tee diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst new file mode 100644 index 000000000000..b448ea3db71d --- /dev/null +++ b/Documentation/security/tpm/tpm_tis.rst @@ -0,0 +1,46 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +TPM FIFO interface driver +========================= + +TCG PTP Specification defines two interface types: FIFO and CRB. The former is +based on sequenced read and write operations, and the latter is based on a +buffer containing the full command or response. + +FIFO (First-In-First-Out) interface is used by the tpm_tis_core dependent +drivers. Originally Linux had only a driver called tpm_tis, which covered +memory mapped (aka MMIO) interface but it was later on extended to cover other +physical interfaces supported by the TCG standard. + +For legacy compliance the original MMIO driver is called tpm_tis and the +framework for FIFO drivers is named as tpm_tis_core. The postfix "tis" in +tpm_tis comes from the TPM Interface Specification, which is the hardware +interface specification for TPM 1.x chips. + +Communication is based on a 20 KiB buffer shared by the TPM chip through a +hardware bus or memory map, depending on the physical wiring. The buffer is +further split into five equal-size 4 KiB buffers, which provide equivalent +sets of registers for communication between the CPU and TPM. These +communication endpoints are called localities in the TCG terminology. + +When the kernel wants to send commands to the TPM chip, it first reserves +locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is +cleared by the chip when the access is granted. Once it completes its +communication, the kernel writes the TPM_ACCESS.activeLocality bit. This +informs the chip that the locality has been relinquished. + +Pending localities are served in order by the chip in descending order, one at +a time: + +- Locality 0 has the lowest priority. +- Locality 5 has the highest priority. + +Further information on the purpose and meaning of the localities can be found +in section 3.2 of the TCG PC Client Platform TPM Profile Specification. + +References +========== + +TCG PC Client Platform TPM Profile (PTP) Specification +https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
Based recent discussions on LKML, provide preliminary bits of tpm_tis_core dependent drivers. Includes only bare essentials but can be extended later on case by case. This way some people may even want to read it later on. Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> --- v4: - Extended the text to address some of Stefan's concerns with v2. - Had to unfortunately remove Randy's reviewed-by because of this, given the amount of text added. v3: - Fixed incorrect buffer size: https://lore.kernel.org/linux-integrity/d957dbd3-4975-48d7-abc5-1a01c0959ea3@linux.ibm.com/ v2: - Fixed errors reported by Randy: https://lore.kernel.org/all/aed28265-d677-491a-a045-24b351854b24@infradead.org/ - Improved the text a bit to have a better presentation. --- Documentation/security/tpm/index.rst | 1 + Documentation/security/tpm/tpm_tis.rst | 46 ++++++++++++++++++++++++++ 2 files changed, 47 insertions(+) create mode 100644 Documentation/security/tpm/tpm_tis.rst