Re: [PATCH for-6.2] hw/arm/virt_acpi_build: Generate DBG2 table

[Andrew Jones <drjones@redhat.com>]

On Tue, Aug 10, 2021 at 12:25:07PM +0200, Eric Auger wrote:
> Hello Ard,
> On 8/10/21 11:36 AM, Ard Biesheuvel wrote:
> > On Tue, 10 Aug 2021 at 10:31, Eric Auger <eric.auger@redhat.com> wrote:
> >> ARM SBBR specification mandates DBG2 table (Debug Port Table 2).
> >> this latter allows to describe one or more debug ports.
> >>
> >> Generate an DBG2 table featuring a single debug port, the PL011.
> >>
> >> The DBG2 specification can be found at:
> >> https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/acpi-debug-port-table?redirectedfrom=MSDN
> >>
> > Have the legal issues around this table been resolved in the mean
> > time?
> I don't know exactly what they are. Adding Al and Jon in the loop they
> have more information about this.
> How did you resolve the issue for EDK2
> (DynamicTablesPkg/Library/Acpi/Arm/AcpiDbg2LibArm/Dbg2Generator.c)?
> >  Also, any clue why this table is mandatory to begin with? The
> > SBBR has been very trigger happy lately with making things mandatory
> > that aren't truly required from a functional perspective.
> It seems there are kernel FW test suites that check all mandated tables
> are available and they currently fail for ARM virt.
> Indeed from a function pov, I don't know much about its usage on ARM.

There's also a bug with getting console output on tty0 with graphical VMs

https://bugzilla.redhat.com/show_bug.cgi?id=1661288

Discussion that includes DBG2 as a possible solution starts around comment
47. I just skimmed the BZ again though and there doesn't appear to be a
clear consensus that DBG2 is the solution.

Thanks,
drew

> 
> Maybe the SBBR spec should not flag the DBG2 as mandatory and test
> suites shall be updated. I think this should be clarified at ARM then,
> all the more so if there are legal issues as its spec is owned by Microsoft?
> 
> Thanks
> 
> Eric
> >
> >
> >> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> >>
> >> ---
> >>
> >> Tested by comparing the content with the table generated
> >> by EDK2 along with the SBSA-REF machine (code generated by
> >> DynamicTablesPkg/Library/Acpi/Arm/AcpiDbg2LibArm/Dbg2Generator.c).
> >>
> >> I reused the Generic Address Structure filled by QEMU in the SPCR, ie.
> >> bit_width = 8 and byte access. While EDK2 sets bit_width = 32 and
> >> dword access. Also the name exposed by acpica tools is different:
> >> 'COM0' in my case where '\_SB.COM0' in SBSA-REF case?
> >> ---
> >>  hw/arm/virt-acpi-build.c    | 77 ++++++++++++++++++++++++++++++++++++-
> >>  include/hw/acpi/acpi-defs.h | 50 ++++++++++++++++++++++++
> >>  2 files changed, 126 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> >> index 037cc1fd82..35f27b41df 100644
> >> --- a/hw/arm/virt-acpi-build.c
> >> +++ b/hw/arm/virt-acpi-build.c
> >> @@ -563,6 +563,78 @@ build_gtdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> >>                   vms->oem_table_id);
> >>  }
> >>
> >> +#define ACPI_DBG2_PL011_UART_LENGTH 0x1000
> >> +
> >> +/* DBG2 */
> >> +static void
> >> +build_dbg2(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> >> +{
> >> +    int addr_offset, addrsize_offset, namespace_offset, namespace_length;
> >> +    const MemMapEntry *uart_memmap = &vms->memmap[VIRT_UART];
> >> +    struct AcpiGenericAddress *base_address;
> >> +    int dbg2_start = table_data->len;
> >> +    AcpiDbg2Device *dbg2dev;
> >> +    char name[] = "COM0";
> >> +    AcpiDbg2Table *dbg2;
> >> +    uint32_t *addr_size;
> >> +    uint8_t *namespace;
> >> +
> >> +    dbg2 = acpi_data_push(table_data, sizeof *dbg2);
> >> +    dbg2->info_offset = sizeof *dbg2;
> >> +    dbg2->info_count = 1;
> >> +
> >> +    /* debug device info structure */
> >> +
> >> +    dbg2dev = acpi_data_push(table_data, sizeof(AcpiDbg2Device));
> >> +
> >> +    dbg2dev->revision = 0;
> >> +    namespace_length = sizeof name;
> >> +    dbg2dev->length = sizeof *dbg2dev + sizeof(struct AcpiGenericAddress) +
> >> +                      4 + namespace_length;
> >> +    dbg2dev->register_count = 1;
> >> +
> >> +    addr_offset = sizeof *dbg2dev;
> >> +    addrsize_offset = addr_offset + sizeof(struct AcpiGenericAddress);
> >> +    namespace_offset = addrsize_offset + 4;
> >> +
> >> +    dbg2dev->namepath_length = cpu_to_le16(namespace_length);
> >> +    dbg2dev->namepath_offset = cpu_to_le16(namespace_offset);
> >> +    dbg2dev->oem_data_length = cpu_to_le16(0);
> >> +    dbg2dev->oem_data_offset = cpu_to_le16(0); /* No OEM data is present */
> >> +    dbg2dev->port_type = cpu_to_le16(ACPI_DBG2_SERIAL_PORT);
> >> +    dbg2dev->port_subtype = cpu_to_le16(ACPI_DBG2_ARM_PL011);
> >> +
> >> +    dbg2dev->base_address_offset = cpu_to_le16(addr_offset);
> >> +    dbg2dev->address_size_offset = cpu_to_le16(addrsize_offset);
> >> +
> >> +    /*
> >> +     * variable length content:
> >> +     * BaseAddressRegister[1]
> >> +     * AddressSize[1]
> >> +     * NamespaceString[1]
> >> +     */
> >> +
> >> +    base_address = acpi_data_push(table_data,
> >> +                                  sizeof(struct AcpiGenericAddress));
> >> +
> >> +    base_address->space_id = AML_SYSTEM_MEMORY;
> >> +    base_address->bit_width = 8;
> >> +    base_address->bit_offset = 0;
> >> +    base_address->access_width = 1;
> >> +    base_address->address = cpu_to_le64(uart_memmap->base);
> >> +
> >> +    addr_size = acpi_data_push(table_data, sizeof *addr_size);
> >> +    *addr_size = cpu_to_le32(ACPI_DBG2_PL011_UART_LENGTH);
> >> +
> >> +    namespace = acpi_data_push(table_data, namespace_length);
> >> +    memcpy(namespace, name, namespace_length);
> >> +
> >> +    build_header(linker, table_data,
> >> +                 (void *)(table_data->data + dbg2_start), "DBG2",
> >> +                 table_data->len - dbg2_start, 3, vms->oem_id,
> >> +                 vms->oem_table_id);
> >> +}
> >> +
> >>  /* MADT */
> >>  static void
> >>  build_madt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> >> @@ -790,7 +862,7 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
> >>      dsdt = tables_blob->len;
> >>      build_dsdt(tables_blob, tables->linker, vms);
> >>
> >> -    /* FADT MADT GTDT MCFG SPCR pointed to by RSDT */
> >> +    /* FADT MADT GTDT MCFG SPCR DBG2 pointed to by RSDT */
> >>      acpi_add_table(table_offsets, tables_blob);
> >>      build_fadt_rev5(tables_blob, tables->linker, vms, dsdt);
> >>
> >> @@ -813,6 +885,9 @@ void virt_acpi_build(VirtMachineState *vms, AcpiBuildTables *tables)
> >>      acpi_add_table(table_offsets, tables_blob);
> >>      build_spcr(tables_blob, tables->linker, vms);
> >>
> >> +    acpi_add_table(table_offsets, tables_blob);
> >> +    build_dbg2(tables_blob, tables->linker, vms);
> >> +
> >>      if (vms->ras) {
> >>          build_ghes_error_table(tables->hardware_errors, tables->linker);
> >>          acpi_add_table(table_offsets, tables_blob);
> >> diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
> >> index cf9f44299c..bdb2ebed2c 100644
> >> --- a/include/hw/acpi/acpi-defs.h
> >> +++ b/include/hw/acpi/acpi-defs.h
> >> @@ -618,4 +618,54 @@ struct AcpiIortRC {
> >>  } QEMU_PACKED;
> >>  typedef struct AcpiIortRC AcpiIortRC;
> >>
> >> +/* DBG2 */
> >> +
> >> +/* Types for port_type field above */
> >> +
> >> +#define ACPI_DBG2_SERIAL_PORT       0x8000
> >> +#define ACPI_DBG2_1394_PORT         0x8001
> >> +#define ACPI_DBG2_USB_PORT          0x8002
> >> +#define ACPI_DBG2_NET_PORT          0x8003
> >> +
> >> +/* Subtypes for port_subtype field above */
> >> +
> >> +#define ACPI_DBG2_16550_COMPATIBLE  0x0000
> >> +#define ACPI_DBG2_16550_SUBSET      0x0001
> >> +#define ACPI_DBG2_ARM_PL011         0x0003
> >> +#define ACPI_DBG2_ARM_SBSA_32BIT    0x000D
> >> +#define ACPI_DBG2_ARM_SBSA_GENERIC  0x000E
> >> +#define ACPI_DBG2_ARM_DCC           0x000F
> >> +#define ACPI_DBG2_BCM2835           0x0010
> >> +
> >> +#define ACPI_DBG2_1394_STANDARD     0x0000
> >> +
> >> +#define ACPI_DBG2_USB_XHCI          0x0000
> >> +#define ACPI_DBG2_USB_EHCI          0x0001
> >> +
> >> +/* Debug Device Information Subtable */
> >> +
> >> +struct AcpiDbg2Device {
> >> +    uint8_t  revision;
> >> +    uint16_t length;
> >> +    uint8_t  register_count; /* Number of base_address registers */
> >> +    uint16_t namepath_length;
> >> +    uint16_t namepath_offset;
> >> +    uint16_t oem_data_length;
> >> +    uint16_t oem_data_offset;
> >> +    uint16_t port_type;
> >> +    uint16_t port_subtype;
> >> +    uint8_t  reserved[2];
> >> +    uint16_t base_address_offset;
> >> +    uint16_t address_size_offset;
> >> +}  QEMU_PACKED;
> >> +typedef struct AcpiDbg2Device AcpiDbg2Device;
> >> +
> >> +struct AcpiDbg2Table {
> >> +    ACPI_TABLE_HEADER_DEF /* ACPI common table header */
> >> +    uint32_t info_offset; /* offset to the first debug struct */
> >> +    uint32_t info_count;  /* number of debug device info struct entries */
> >> +    uint8_t  dbg2_device_info[];
> >> +} QEMU_PACKED;
> >> +typedef struct AcpiDbg2Table AcpiDbg2Table;
> >> +
> >>  #endif
> >> --
> >> 2.26.3
> >>
>