"Michael S. Tsirkin" <m...@redhat.com> wrote on 07/30/2014 11:20:41 AM:
> From: "Michael S. Tsirkin" <m...@redhat.com> > To: Stefan Berger/Watson/IBM@IBMUS > Cc: Laszlo Ersek <ler...@redhat.com>, qemu-devel@nongnu.org, Stefan > Berger <stef...@linux.vnet.ibm.com> > Date: 07/30/2014 11:20 AM > Subject: Re: [PATCH v2] Add ACPI tables for TPM > > On Wed, Jul 30, 2014 at 11:10:27AM -0400, 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); > > > > Regards, > > Stefan > > > Becase FACS is an ACPI table. So BIOS allocates it > from E820_RESERVED at the moment but it does not have to, > it could mark it with E820_ACPI. > Guest can then interpret the tables and then release the > memory if it wishes. > > If you want to do it for TCPA you must tell bios that > this is not ACPI memory. I see. Presumably the whole slew of FADT, FACS, RSDP, & RSDT would need a similar tag to keep the S3 resume vector around? Stefan
