Re: [Qemu-devel] [PATCH v3 3/4] acpi: build TPM Physical Presence interface

[Laszlo Ersek]

On 06/20/18 16:35, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jun 20, 2018 at 4:08 PM, Michael S. Tsirkin <address@hidden> wrote:
>> On Tue, May 15, 2018 at 02:14:32PM +0200, Marc-André Lureau wrote:
>>> From: Stefan Berger <address@hidden>
>>>
>>> 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 <address@hidden>
>>>
>>> ---
>>>
>>> v4 (Marc-André):
>>>  - replace 'DerefOf (FUNC [N])' with a function, to fix Windows ACPI
>>>     handling.
>>>  - replace 'return Package (..) {} ' with scoped variables, to fix
>>>    Windows ACPI handling.
>>>
>>> v3:
>>>  - add support for PPI to CRB
>>>  - split up OperationRegion TPPI into two parts, one containing
>>>    the registers (TPP1) and the other one the flags (TPP2); switched
>>>    the order of the flags versus registers in the code
>>>  - adapted ACPI code to small changes to the array of flags where
>>>    previous flag 0 was removed and now shifting right wasn't always
>>>    necessary anymore
>>>
>>> v2:
>>>  - get rid of FAIL variable; function 5 was using it and always
>>>    returns 0; the value is related to the ACPI function call not
>>>    a possible failure of the TPM function call.
>>>  - extend shared memory data structure with per-opcode entries
>>>    holding flags and use those flags to determine what to return
>>>    to caller
>>>  - implement interface version 1.3
>>> ---
>>>  include/hw/acpi/tpm.h |  21 +++
>>>  hw/i386/acpi-build.c  | 294 +++++++++++++++++++++++++++++++++++++++++-
>>>  2 files changed, 314 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/hw/acpi/tpm.h b/include/hw/acpi/tpm.h
>>> index f79d68a77a..fc53f08827 100644
>>> --- a/include/hw/acpi/tpm.h
>>> +++ b/include/hw/acpi/tpm.h
>>> @@ -196,4 +196,25 @@ REG32(CRB_DATA_BUFFER, 0x80)
>>>  #define TPM_PPI_VERSION_NONE        0
>>>  #define TPM_PPI_VERSION_1_30        1
>>>
>>> +struct tpm_ppi {
>>
>> The name violate the coding style.
> 
> That's easy to change. Stefan could do it on commit if the rest of the
> patch is unchanged.
>>
>>
>>> +    uint8_t  func[256];      /* 0x000: per TPM function implementation 
>>> flags;
>>> +                                       set by BIOS */
>>> +/* whether function is blocked by BIOS settings; bits 0, 1, 2 */
>>> +#define TPM_PPI_FUNC_NOT_IMPLEMENTED     (0 << 0)
>>> +#define TPM_PPI_FUNC_BIOS_ONLY           (1 << 0)
>>> +#define TPM_PPI_FUNC_BLOCKED             (2 << 0)
>>> +#define TPM_PPI_FUNC_ALLOWED_USR_REQ     (3 << 0)
>>> +#define TPM_PPI_FUNC_ALLOWED_USR_NOT_REQ (4 << 0)
>>> +#define TPM_PPI_FUNC_MASK                (7 << 0)
>>> +    uint8_t ppin;            /* 0x100 : set by BIOS */
>>
>> Are you sure it's right? Below ints will all end up misaligned ...
> 
> Hmm. Sadly, we didn't noticed when doing the edk2 part either. If we
> change it in qemu, we will have to change it in edk2 as well

I don't see why the misalignment is a problem. AIUI functionally it
shouldn't be an issue, and performance is not critical.

We did make sure the struct was packed in edk2 too.

Thanks,
Laszlo

> 
>>> +    uint32_t ppip;           /* 0x101 : set by ACPI; not used */
>>> +    uint32_t pprp;           /* 0x105 : response from TPM; set by BIOS */
>>> +    uint32_t pprq;           /* 0x109 : opcode; set by ACPI */
>>> +    uint32_t pprm;           /* 0x10d : parameter for opcode; set by ACPI 
>>> */
>>> +    uint32_t lppr;           /* 0x111 : last opcode; set by BIOS */
>>> +    uint32_t fret;           /* 0x115 : set by ACPI; not used */
>>> +    uint8_t res1[0x40];      /* 0x119 : reserved for future use */
>>> +    uint8_t next_step;       /* 0x159 : next step after reboot; set by 
>>> BIOS */
>>> +} QEMU_PACKED;
>>> +
>>>  #endif /* HW_ACPI_TPM_H */
>>
>> Igor could you pls take a quick look at the rest?
>>
>> --
>> MST
>>
> 
> thanks
> 
>