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? -- MST
