On 07/30/14 17:52, Michael S. Tsirkin wrote: > On Wed, Jul 30, 2014 at 05:37:26PM +0200, Laszlo Ersek wrote: >> On 07/30/14 17:10, Stefan Berger wrote: >>> Laszlo Ersek <ler...@redhat.com> wrote on 07/30/2014 10:36:38 AM: >>> >>>> From: Laszlo Ersek <ler...@redhat.com> >>>> To: "Michael S. Tsirkin" <m...@redhat.com>, Stefan Berger/Watson/IBM@IBMUS >>>> Cc: qemu-devel@nongnu.org, Stefan Berger <stef...@linux.vnet.ibm.com> >>>> Date: 07/30/2014 10:36 AM >>>> Subject: Re: [PATCH v2] Add ACPI tables for TPM >>>> >>>> On 07/30/14 15:20, Michael S. Tsirkin wrote: >>>>> On Tue, Jul 29, 2014 at 06:52:19AM -0400, Stefan Berger wrote: >>>>>> From: Stefan Berger <stef...@linux.vnet.ibm.com> >>>>>> >>>>>> Add an SSDT ACPI table for the TPM device. >>>>>> Add a TCPA table for BIOS logging area when a TPM is being used. >>>>>> >>>>>> The latter follows this spec here: >>>>>> >>>>>> http://www.trustedcomputinggroup.org/files/static_page_files/ >>>> DCD4188E-1A4B-B294-D050A155FB6F7385/ >>>> TCG_ACPIGeneralSpecification_PublicReview.pdf >>>> >>>> (Thanks for CC'ing me, Michael.) >>>> >>>> I skimmed this spec. >>>> >>>>>> +static void >>>>>> +build_tpm_tcpa(GArray *table_data, GArray *linker) >>>>>> +{ >>>>>> + Acpi20Tcpa *tcpa; >>>>>> + uint32_t log_area_minimum_length = TPM_LOG_AREA_MINIMUM_SIZE; >>>>>> + uint64_t log_area_start_address; >>>>>> + size_t len = log_area_minimum_length + sizeof(*tcpa); >>>>>> + >>>>>> + log_area_start_address = table_data->len + sizeof(*tcpa); >>>>>> + >>>>>> + tcpa = acpi_data_push(table_data, len); >>>>>> + >>>>>> + tcpa->platform_class = cpu_to_le16(TPM_TCPA_ACPI_CLASS_CLIENT); >>>>>> + tcpa->log_area_minimum_length = >>> cpu_to_le32(log_area_minimum_length); >>>>>> + tcpa->log_area_start_address = >>> cpu_to_le64(log_area_start_address); >>>>>> + >>>>>> + /* LASA address to be filled by Guest linker */ >>>>> >>>>> Hmm, you are simply allocating log area as part of the ACPI table. It >>>>> works because bios happens to allocate tables from high memory. >>>>> But I think this is a problem in practice because >>>>> bios is allowed to allocate acpi memory differently. >>>>> On the other hand log presumably needs to reside in >>>>> physical memory somewhere. >>>>> >>>>> If you need bios to allocate this memory, then we will >>>>> need a new allocation type for this, add it to linker >>>>> in bios and qemu. >>>>> >>>>> Alternatively, find some other way to get hold of >>>>> physical memory. >>>>> Is there a way to disable the log completely? >>>>> As defined in your patch, I doubt there's anything there, ever .. >>>>> >>>>> >>>>> >>>>>> + bios_linker_loader_add_pointer(linker, ACPI_BUILD_TABLE_FILE, >>>>>> + ACPI_BUILD_TABLE_FILE, >>>>>> + table_data, >>>> &tcpa->log_area_start_address, >>>>>> + >>> sizeof(tcpa->log_area_start_address)); >>>>>> + build_header(linker, table_data, >>>>>> + (void *)tcpa, "TCPA", sizeof(*tcpa), 2); >>>>>> +} >>>> >>>> So here's my understanding. The spec referenced above describes three >>>> ACPI tables: two (client vs. server) for TPM 1.2, and a third one >>>> (usable by both client & server platforms) for TPM 2.0. >>>> >>>> The code above prepares a TPM 1.2 table. (Signature: "TCPA".) >>>> >>>> This table has a field called LASA (Log Area Start Address) which points >>>> to somewhere in (guest-)physical memory. The patch adds a "dummy range" >>>> to the end of the TCPA table itself, and asks the linker to set LASA to >>>> the beginning of that range. >>>> >>>> This won't work in OVMF, and not just because of the reason that Michael >>>> mentions (ie. because the firmware, in particular SeaBIOS, might >>>> allocate the TCPA table in an area that is unsuitable as LASA target). >>>> >>>> Rather, in OVMF this won't work because OVMF doesn't implement the >>>> linking part of the linker. The *generic* edk2 protocol >>>> (EFI_ACPI_TABLE_PROTOCOL, which is coded outside of OVMF) that OVMF uses >>>> (as a client) to install ACPI tables in guest-phys memory requires >>>> tables to be passed in one-by-one. >>>> >>>> The EFI_ACPI_TABLE_PROTOCOL implementation in edk2 handles *some* >>>> well-known tables specially. It has knowledge of their internal >>>> pointers, and when you install an ACPI table, EFI_ACPI_TABLE_PROTOCOL >>>> updates pointers automatically. (For example when you install the FACS, >>>> the protocol links it automatically into FACP.) >>>> >>>> The EFI_ACPI_TABLE_PROTOCOL implementation in edk2 doesn't seem to know >>>> anything about the TCPA table, let alone the unstructured (?) TCG event >>>> log that is pointed-to by TCPA.LASA. >>>> >>>> (I grepped for the TCPA signature, >>>> >>> EFI_ACPI_5_0_TRUSTED_COMPUTING_PLATFORM_ALLIANCE_CAPABILITIES_TABLE_SIGNATURE.) >>>> >>>> This means that if you pass down a TCPA table, OVMF will install it >>>> right now, but TCPA.LASA will be bogus. >>>> >>>> If I wanted to implement the complete linker as Michael envisioned it, >>>> then I'd have to avoid edk2's EFI_ACPI_TABLE_PROTOCOL, and implement >>>> ACPI table installation from zero, trying to mimic the SeaBIOS client >>>> code, but in a way that matches the UEFI environment. I'm not ready to >>>> do that. Definitely not without an "official" human-language >>>> specification of the linker-loader interface. >>>> >>>> I skimmed the patch but I'm not sure what exactly the TPM emulation in >>>> qemu depends on. Is it a command line option? Is it default for some >>>> machine types? >>>> >>>> Alternatively, I could recognize the TCPA signature in OVMF when parsing >>>> the ACPI blobs for table headers, and filter it out. >>> >>> This is the code for what I would call 'pointer relocation'. The TCPA >>> table is not the only place where this is used, but why is it an issue >>> there while not with the following? >>> >>> fadt->firmware_ctrl = cpu_to_le32(facs); >>> /* FACS address to be filled by Guest linker */ >>> bios_linker_loader_add_pointer(linker, ACPI_BUILD_TABLE_FILE, >>> ACPI_BUILD_TABLE_FILE, >>> table_data, &fadt->firmware_ctrl, >>> sizeof fadt->firmware_ctrl); >> >> (Responding wrt. to OVMF:) because EFI_ACPI_TABLE_PROTOCOL special cases >> the installation of FACS. This is visible both in the UEFI >> specification, and in the edk2 implementation. >> >> That is, OVMF can avoid relocating the "fadt->firmware_ctrl" pointer, >> because edk2's EFI_ACPI_TABLE_PROTOCOL will do that automatically, when >> OVMF requests the installation of FACS. >> >> No such special case exists for the installation of the TCG event log >> area (which is by itself not even an ACPI table as I gather). *If* the >> TCG event log were an ACPI table in its own right, *and* edk2's >> EFI_ACPI_TABLE_PROTOCOL implementation had a special case for it, then >> when OVMF installed the event log, EFI_ACPI_TABLE_PROTOCOL would update >> TCPA.LASA to it. >> >> Thanks >> Laszlo > > How does EFI want to handle TCPA? Does caller allocate it > log and fill in the address?
TPM 1.2 seems to be completely absent from edk2, so I have no clue. TPM 2.0 appears to be supported, but I already grepped edk2 for how it handles the related ACPI table(s), and it doesn't. As far as I can see. In the long term, if you can find a way to make it work with SeaBIOS, inside the linker/loader framework, that should work under OVMF as well. I hope. Famous last words. Laszlo
