acpi: build TPM Physical Presence interface

The TPM Physical Presence interface consists of an ACPI part, a shared
memory part, and code in the firmware. Users can send messages to the
firmware by writing a code into the shared memory through invoking the
ACPI code. When a reboot happens, the firmware looks for the code and
acts on it by sending sequences of commands to the TPM.

This patch adds the ACPI code. It is similar to the one in EDK2 but doesn't
assume that SMIs are necessary to use. It uses a similar datastructure for
the shared memory as EDK2 does so that EDK2 and SeaBIOS could both make use
of it. I extended the shared memory data structure with an array of 256
bytes, one for each code that could be implemented. The array contains
flags describing the individual codes. This decouples the ACPI implementation
from the firmware implementation.

The underlying TCG specification is accessible from the following page.

https://trustedcomputinggroup.org/tcg-physical-presence-interface-specification/

This patch implements version 1.30.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
[ Marc-André - ACPI code improvements and windows fixes ]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 83 insertions, 0 deletions

diff --git a/docs/specs/tpm.txt b/docs/specs/tpm.txt
index e4bb094700..424d1511fc 100644
--- a/docs/specs/tpm.txt
+++ b/docs/specs/tpm.txt
@@ -76,6 +76,89 @@ URL:
 
 https://trustedcomputinggroup.org/tcg-acpi-specification/
 
+== ACPI PPI Interface ==
+
+QEMU supports the Physical Presence Interface (PPI) for TPM 1.2 and TPM 2. This
+interface requires ACPI and firmware support. The specification can be found at
+the following URL:
+
+https://trustedcomputinggroup.org/resource/tcg-physical-presence-interface-specification/
+
+PPI enables a system administrator (root) to request a modification to the
+TPM upon reboot. The PPI specification defines the operation requests and the
+actions the firmware has to take. The system administrator passes the operation
+request number to the firmware through an ACPI interface which writes this
+number to a memory location that the firmware knows. Upon reboot, the firmware
+finds the number and sends commands to the the TPM. The firmware writes the TPM
+result code and the operation request number to a memory location that ACPI can
+read from and pass the result on to the administrator.
+
+The PPI specification defines a set of mandatory and optional operations for
+the firmware to implement. The ACPI interface also allows an administrator to
+list the supported operations. In QEMU the ACPI code is generated by QEMU, yet
+the firmware needs to implement support on a per-operations basis, and
+different firmwares may support a different subset. Therefore, QEMU introduces
+the virtual memory device for PPI where the firmware can indicate which
+operations it supports and ACPI can enable the ones that are supported and
+disable all others. This interface lies in main memory and has the following
+layout:
+
+ +----------+--------+--------+-------------------------------------------+
+ |  Field   | Length | Offset | Description                               |
+ +----------+--------+--------+-------------------------------------------+
+ | func     |  0x100 |  0x000 | Firmware sets values for each supported   |
+ |          |        |        | operation. See defined values below.      |
+ +----------+--------+--------+-------------------------------------------+
+ | ppin     |   0x1  |  0x100 | SMI interrupt to use. Set by firmware.    |
+ |          |        |        | Not supported.                            |
+ +----------+--------+--------+-------------------------------------------+
+ | ppip     |   0x4  |  0x101 | ACPI function index to pass to SMM code.  |
+ |          |        |        | Set by ACPI. Not supported.               |
+ +----------+--------+--------+-------------------------------------------+
+ | pprp     |   0x4  |  0x105 | Result of last executed operation. Set by |
+ |          |        |        | firmware. See function index 5 for values.|
+ +----------+--------+--------+-------------------------------------------+
+ | pprq     |   0x4  |  0x109 | Operation request number to execute. See  |
+ |          |        |        | 'Physical Presence Interface Operation    |
+ |          |        |        | Summary' tables in specs. Set by ACPI.    |
+ +----------+--------+--------+-------------------------------------------+
+ | pprm     |   0x4  |  0x10d | Operation request optional parameter.     |
+ |          |        |        | Values depend on operation. Set by ACPI.  |
+ +----------+--------+--------+-------------------------------------------+
+ | lppr     |   0x4  |  0x111 | Last executed operation request number.   |
+ |          |        |        | Copied from pprq field by firmware.       |
+ +----------+--------+--------+-------------------------------------------+
+ | fret     |   0x4  |  0x115 | Result code from SMM function.            |
+ |          |        |        | Not supported.                            |
+ +----------+--------+--------+-------------------------------------------+
+ | res1     |  0x40  |  0x119 | Reserved for future use                   |
+ +----------+--------+--------+-------------------------------------------+
+ | next_step|   0x1  |  0x159 | Operation to execute after reboot by      |
+ |          |        |        | firmware. Used by firmware.               |
+ +----------+--------+--------+-------------------------------------------+
+
+   The following values are supported for the 'func' field. They correspond
+   to the values used by ACPI function index 8.
+
+ +----------+-------------------------------------------------------------+
+ | value    | Description                                                 |
+ +----------+-------------------------------------------------------------+
+ | 0        | Operation is not implemented.                               |
+ +----------+-------------------------------------------------------------+
+ | 1        | Operation is only accessible through firmware.              |
+ +----------+-------------------------------------------------------------+
+ | 2        | Operation is blocked for OS by firmware configuration.      |
+ +----------+-------------------------------------------------------------+
+ | 3        | Operation is allowed and physically present user required.  |
+ +----------+-------------------------------------------------------------+
+ | 4        | Operation is allowed and physically present user is not     |
+ |          | required.                                                   |
+ +----------+-------------------------------------------------------------+
+
+The location of the table is given by the fw_cfg tpmppi_address field.
+The PPI memory region size is 0x400 (TPM_PPI_ADDR_SIZE) to leave
+enough room for future updates.
+
 
 QEMU files related to TPM ACPI tables:
  - hw/i386/acpi-build.c