Re: [PATCH v4 07/10] hw/i386: declare ACPI mother board resource for MMCONFIG region

[Igor Mammedov]

On Mon, 15 Feb 2021 17:04:12 -0800
isaku.yamahata@gmail.com wrote:

> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> Declare PNP0C01 device to reserve MMCONFIG region to conform to the
> spec better and play nice with guest BIOSes/OSes.
> 
> According to PCI Firmware Specification[0], MMCONFIG region must be
> reserved by declaring a motherboard resource. It's optional to reserve
> the region in memory map by Int 15 E820h or EFIGetMemoryMap.
> Guest Linux checks if the MMCFG region is reserved by bios memory map
> or ACPI resource. If it's not reserved, Linux falls back to legacy PCI
> configuration access.
> 
> TDVF [1] [2] doesn't reserve MMCONFIG the region in memory map.
> On the other hand OVMF reserves it in memory map without declaring a
> motherboard resource. With memory map reservation, linux guest uses
> MMCONFIG region. However it doesn't comply to PCI Firmware
> specification.
> 
> [0] PCI Firmware specification Revision 3.2
>   4.1.2 MCFG Table Description table 4-2 NOTE 2
>   If the operating system does not natively comprehend reserving the
>   MMCFG region, The MMCFG region must e reserved by firmware. ...
>   For most systems, the mortheroard resource would appear at the root
>   of the ACPI namespace (under \_SB)...
>   The resource can optionally be returned in Int15 E820h or
>   EFIGetMemoryMap as reserved memory but must always be reported
>   through ACPI as a motherboard resource
> 
> [1] TDX: Intel Trust Domain Extension
>     
> https://software.intel.com/content/www/us/en/develop/articles/intel-trust-domain-extensions.html
> [2] TDX Virtual Firmware
>     https://github.com/tianocore/edk2-staging/tree/TDVF
> 
> The change to DSDT is as follows.
> 
> @@ -68,32 +68,51 @@
> 
>                      If ((CDW3 != Local0))
>                      {
>                          CDW1 |= 0x10
>                      }
> 
>                      CDW3 = Local0
>                  }
>                  Else
>                  {
>                      CDW1 |= 0x04
>                  }
> 
>                  Return (Arg3)
>              }
>          }
> +
> +        Device (DRAC)
> +        {
> +            Name (_HID, "PNP0C01" /* System Board */)  // _HID: Hardware ID
> +            Name (RBUF, ResourceTemplate ()
> +            {
> +                DWordMemory (ResourceProducer, PosDecode, MinFixed, 
> MaxFixed, NonCacheable, ReadWrite,
> +                    0x00000000,         // Granularity
> +                    0xB0000000,         // Range Minimum
> +                    0xB0000000,         // Range Maximum
> +                    0x00000000,         // Translation Offset
> +                    0x10000000,         // Length
> +                    ,, , AddressRangeMemory, TypeStatic)
> +            })
> +            Method (_CRS, 0, Serialized)  // _CRS: Current Resource Settings
> +            {
> +                Return (RBUF) /* \_SB_.DRAC.RBUF */
> +            }
> +        }
>      }
> 
>      Scope (_SB)
>      {
>          Device (HPET)
>          {
>              Name (_HID, EisaId ("PNP0103") /* HPET System Timer */)  // 
> _HID: Hardware ID
>              Name (_UID, Zero)  // _UID: Unique ID
>              OperationRegion (HPTM, SystemMemory, 0xFED00000, 0x0400)
>              Field (HPTM, DWordAcc, Lock, Preserve)
>              {
>                  VEND,   32,
>                  PRD,    32
>              }
> 
>              Method (_STA, 0, NotSerialized)  // _STA: Status
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>  hw/i386/acpi-build.c | 55 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index e3386ae674..30326f69b3 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1072,6 +1072,55 @@ static void build_q35_pci0_int(Aml *table)
>      aml_append(table, sb_scope);
>  }
>  
> +static Aml *build_q35_dram_controller(AcpiMcfgInfo *mcfg)
> +{
> +    Aml *dev;
> +    Aml *rbuf;
> +    Aml *resource_template;
> +    Aml *rbuf_name;
> +    Aml *crs;
> +
> +    /* DRAM controller */
> +    dev = aml_device("DRAC");
> +    aml_append(dev, aml_name_decl("_HID", aml_string("PNP0C01")));
> +
> +    resource_template = aml_resource_template();
> +    if (mcfg->base + mcfg->size - 1 >= (1ULL << 32)) {
> +        aml_append(resource_template,
> +                   aml_qword_memory(AML_POS_DECODE,
> +                                    AML_MIN_FIXED,
> +                                    AML_MAX_FIXED,
> +                                    AML_NON_CACHEABLE,
> +                                    AML_READ_WRITE,
> +                                    0x0000000000000000,
> +                                    mcfg->base,
> +                                    mcfg->base,
                                here       ^^^

> +        aml_append(resource_template,
> +                   aml_dword_memory(AML_POS_DECODE,
> +                                    AML_MIN_FIXED,
> +                                    AML_MAX_FIXED,
> +                                    AML_NON_CACHEABLE,
> +                                    AML_READ_WRITE,
> +                                    0x0000000000000000,
> +                                    mcfg->base,
> +                                    mcfg->base,
                             and here   ^^^
please revert it to the way did it in v3,
I was wrong suggesting that for fixed address case.
 
> +                                    0x0000000000000000,
> +                                    mcfg->size));
> +    }

> +    rbuf = aml_name_decl("RBUF", resource_template);
> +    aml_append(dev, rbuf);
> +
> +    crs = aml_method("_CRS", 0, AML_SERIALIZED);
> +    rbuf_name = aml_name("RBUF");
> +    aml_append(crs, aml_return(rbuf_name));
> +    aml_append(dev, crs);
can be simpler if method is replaced with _CRS variable, i.e.:

       aml_append(dev, aml_name_decl("_CRS", resource_template));

> +
> +    return dev;
> +}
> +
>  static void build_q35_isa_bridge(Aml *table)
>  {
>      Aml *dev;
> @@ -1218,6 +1267,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>      PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
>      X86MachineState *x86ms = X86_MACHINE(machine);
>      AcpiMcfgInfo mcfg;
> +    bool mcfg_valid = !!acpi_get_mcfg(&mcfg);
>      uint32_t nr_mem = machine->ram_slots;
>      int root_bus_limit = 0xFF;
>      PCIBus *bus = NULL;
> @@ -1256,6 +1306,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>          aml_append(dev, aml_name_decl("_UID", aml_int(0)));
>          aml_append(dev, build_q35_osc_method());
>          aml_append(sb_scope, dev);
> +        if (mcfg_valid) {
> +            aml_append(sb_scope, build_q35_dram_controller(&mcfg));
> +        }
>  
>          if (pm->smi_on_cpuhp) {
>              /* reserve SMI block resources, IO ports 0xB2, 0xB3 */
> @@ -1386,7 +1439,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>       * the PCI0._CRS.  Add mmconfig to the set so it will be excluded
>       * too.
>       */
> -    if (acpi_get_mcfg(&mcfg)) {
> +    if (mcfg_valid) {
>          crs_range_insert(crs_range_set.mem_ranges,
>                           mcfg.base, mcfg.base + mcfg.size - 1);
>      }