Re: [Qemu-devel] [PATCH v2 2/4] acpi: build QEMU table for PPI virtual memory device

[Laszlo Ersek]

On 01/16/18 16:51, Stefan Berger wrote:
> To avoid having to hard code the base address of the PPI virtual memory
> device we introduce a QEMU ACPI table that holds the base address, if a
> TPM 1.2 or 2 is used. This table gives us flexibility to move the base
> address later on.
> 
> Signed-off-by: Stefan Berger <address@hidden>
> ---
>  hw/i386/acpi-build.c        | 19 +++++++++++++++++++
>  include/hw/acpi/acpi-defs.h |  8 ++++++++
>  2 files changed, 27 insertions(+)

I don't understand how the guest OS is supposed to consume the QEMU
table. The AML code in patch #4 does not seem to consume the QEMU table,
for locating the operation region. I'm not saying that it *should*
consume the QEMU table, only that I'm currently not seeing a use for the
QEMU table.

How is the QEMU table useful? What breaks if we drop it?

(Sorry if we've been through this; then I must have lost context.)

Thanks,
Laszlo

> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 18b939e..522d6d2 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2628,6 +2628,20 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg)
>      return true;
>  }
>  
> +static void build_qemu(GArray *table_data, BIOSLinker *linker,
> +                       TPMVersion tpm_version)
> +{
> +    AcpiTableQemu *qemu = acpi_data_push(table_data, sizeof(*qemu));
> +
> +    if (tpm_version != TPM_VERSION_UNSPEC) {
> +        qemu->tpmppi_addr = TPM_PPI_ADDR_BASE;
> +        qemu->tpm_version = tpm_version;
> +    }
> +
> +    build_header(linker, table_data,
> +                 (void *)qemu, "QEMU", sizeof(*qemu), 1, "QEMU", "CONF");
> +}
> +
>  static
>  void acpi_build(AcpiBuildTables *tables, MachineState *machine)
>  {
> @@ -2734,6 +2748,11 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>                            &pcms->acpi_nvdimm_state, machine->ram_slots);
>      }
>  
> +    if (misc.tpm_version != TPM_VERSION_UNSPEC) {
> +        acpi_add_table(table_offsets, tables_blob);
> +        build_qemu(tables_blob, tables->linker, misc.tpm_version);
> +    }
> +
>      /* Add tables supplied by user (if any) */
>      for (u = acpi_table_first(); u; u = acpi_table_next(u)) {
>          unsigned len = acpi_table_len(u);
> diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
> index 80c8099..98764c1 100644
> --- a/include/hw/acpi/acpi-defs.h
> +++ b/include/hw/acpi/acpi-defs.h
> @@ -573,6 +573,14 @@ struct Acpi20TPM2 {
>  } QEMU_PACKED;
>  typedef struct Acpi20TPM2 Acpi20TPM2;
>  
> +/* QEMU - Custom QEMU table */
> +struct AcpiTableQemu {
> +    ACPI_TABLE_HEADER_DEF
> +    uint32_t tpmppi_addr;
> +    uint8_t tpm_version; /* 1 = 1.2, 2 = 2 */
> +};
> +typedef struct AcpiTableQemu AcpiTableQemu;
> +
>  /* DMAR - DMA Remapping table r2.2 */
>  struct AcpiTableDmar {
>      ACPI_TABLE_HEADER_DEF
>