Re: [PATCH] MdeModulePkg/AcpiTableDxe: Not make FADT.{DSDT, X_DSDT} mutual exclusion

["Fan, Jeff" <jeff.fan@intel.com>]

Tested-by: Jeff Fan <jeff.fan@intel.com>

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Thursday, March 16, 2017 7:59 PM
To: Zeng, Star; edk2-devel@lists.01.org
Cc: Fan, Jeff; Yao, Jiewen
Subject: Re: [PATCH] MdeModulePkg/AcpiTableDxe: Not make FADT.{DSDT,X_DSDT} mutual exclusion

On 03/16/17 09:17, Star Zeng wrote:
> 198a46d768fb90d2f9b16e26451b4814e7469eaf improved the DSDT and X_DSDT 
> fields mutual exclusion by checking FADT revision, but that breaks 
> some OS that has assumption to only consume X_DSDT field even the DSDT 
> address is < 4G.
> 
> To have better compatibility, this patch is to update the code to not 
> make FADT.{DSDT,X_DSDT} mutual exclusion, but always set both DSDT and 
> X_DSDT fields in the FADT when the DSDT address is < 4G.
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Jeff Fan <jeff.fan@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> 
> NOTE: This patch comes out from the discussion at 
> https://lists.01.org/pipermail/edk2-devel/2017-March/008580.html.
> ---
>  .../Acpi/AcpiTableDxe/AcpiTableProtocol.c          | 88 +++++++++-------------
>  1 file changed, 34 insertions(+), 54 deletions(-)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thank you!
Laszlo

> diff --git 
> a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c 
> b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
> index 4bb848df5203..a4fd9aff845d 100644
> --- a/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
> +++ b/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c
> @@ -432,50 +432,6 @@ ReallocateAcpiTableBuffer (  }
>  
>  /**
> -  Determine whether the FADT table passed in as parameter requires 
> mutual
> -  exclusion between the DSDT and X_DSDT fields. (That is, whether 
> there exists
> -  an explicit requirement that at most one of those fields is 
> permitted to be
> -  nonzero.)
> -
> -  @param[in] Fadt  The EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE object to
> -                   check.
> -
> -  @retval TRUE     Fadt requires mutual exclusion between DSDT and X_DSDT.
> -  @retval FALSE    Otherwise.
> -**/
> -BOOLEAN
> -RequireDsdtXDsdtExclusion (
> -  IN EFI_ACPI_3_0_FIXED_ACPI_DESCRIPTION_TABLE *Fadt
> -  )
> -{
> -  //
> -  // Mantis ticket #1393 was addressed in ACPI 5.1 Errata B. 
> Unfortunately, we
> -  // can't tell apart 5.1 Errata A and 5.1 Errata B just from looking 
> at the
> -  // FADT table. Therefore let's require exclusion for table versions >= 5.1.
> -  //
> -  // While this needlessly covers 5.1 and 5.1A too, it is safer to 
> require
> -  // DSDT<->X_DSDT exclusion for lax (5.1, 5.1A) versions of the spec 
> than to
> -  // permit DSDT<->X_DSDT duplication for strict (5.1B) versions of the spec.
> -  //
> -  // The same applies to 6.0 vs. 6.0A. While 6.0 does not require the
> -  // exclusion, 6.0A and 6.1 do. Since we cannot distinguish 6.0 from 
> 6.0A
> -  // based on just the FADT, we lump 6.0 in with the rest of >= 5.1.
> -  //
> -  if ((Fadt->Header.Revision < 5) ||
> -      ((Fadt->Header.Revision == 5) &&
> -       (((EFI_ACPI_5_1_FIXED_ACPI_DESCRIPTION_TABLE *)Fadt)->MinorVersion == 0))) {
> -    //
> -    // version <= 5.0
> -    //
> -    return FALSE;
> -  }
> -  //
> -  // version >= 5.1
> -  //
> -  return TRUE;
> -}
> -
> -/**
>    This function adds an ACPI table to the table list.  It will detect FACS and
>    allocate the correct type of memory and properly align the table.
>  
> @@ -692,11 +648,23 @@ AddTableToList (
>        }
>        if ((UINT64)(UINTN)AcpiTableInstance->Dsdt3 < BASE_4GB) {
>          AcpiTableInstance->Fadt3->Dsdt = (UINT32) (UINTN) AcpiTableInstance->Dsdt3;
> -        if (RequireDsdtXDsdtExclusion (AcpiTableInstance->Fadt3)) {
> -          Buffer64 = 0;
> -        } else {
> -          Buffer64 = AcpiTableInstance->Fadt3->Dsdt;
> -        }
> +        //
> +        // Comment block "the caller installs the tables in "DSDT, FADT" order"
> +        // The below comments are also in "the caller installs the tables in "FADT, DSDT" order" comment block.
> +        //
> +        // The ACPI specification, up to and including revision 5.1 Errata A,
> +        // allows the DSDT and X_DSDT fields to be both set in the FADT.
> +        // (Obviously, this only makes sense if the DSDT address is representable in 4 bytes.)
> +        // Starting with 5.1 Errata B, specifically for Mantis 1393 <https://mantis.uefi.org/mantis/view.php?id=1393>,
> +        // the spec requires at most one of DSDT and X_DSDT fields to be set to a nonzero value,
> +        // but strangely an exception is 6.0 that has no this requirement.
> +        //
> +        // Here we do not make the DSDT and X_DSDT fields mutual exclusion conditionally
> +        // by checking FADT revision, but always set both DSDT and X_DSDT fields in the FADT
> +        // to have better compatibility as some OS may have assumption to only consume X_DSDT
> +        // field even the DSDT address is < 4G.
> +        //
> +        Buffer64 = AcpiTableInstance->Fadt3->Dsdt;
>        } else {
>          AcpiTableInstance->Fadt3->Dsdt = 0;
>          Buffer64 = (UINT64) (UINTN) AcpiTableInstance->Dsdt3; @@ 
> -896,11 +864,23 @@ AddTableToList (
>        if (AcpiTableInstance->Fadt3 != NULL) {
>          if ((UINT64)(UINTN)AcpiTableInstance->Dsdt3 < BASE_4GB) {
>            AcpiTableInstance->Fadt3->Dsdt = (UINT32) (UINTN) AcpiTableInstance->Dsdt3;
> -          if (RequireDsdtXDsdtExclusion (AcpiTableInstance->Fadt3)) {
> -            Buffer64 = 0;
> -          } else {
> -            Buffer64 = AcpiTableInstance->Fadt3->Dsdt;
> -          }
> +          //
> +          // Comment block "the caller installs the tables in "FADT, DSDT" order"
> +          // The below comments are also in "the caller installs the tables in "DSDT, FADT" order" comment block.
> +          //
> +          // The ACPI specification, up to and including revision 5.1 Errata A,
> +          // allows the DSDT and X_DSDT fields to be both set in the FADT.
> +          // (Obviously, this only makes sense if the DSDT address is representable in 4 bytes.)
> +          // Starting with 5.1 Errata B, specifically for Mantis 1393 <https://mantis.uefi.org/mantis/view.php?id=1393>,
> +          // the spec requires at most one of DSDT and X_DSDT fields to be set to a nonzero value,
> +          // but strangely an exception is 6.0 that has no this requirement.
> +          //
> +          // Here we do not make the DSDT and X_DSDT fields mutual exclusion conditionally
> +          // by checking FADT revision, but always set both DSDT and X_DSDT fields in the FADT
> +          // to have better compatibility as some OS may have assumption to only consume X_DSDT
> +          // field even the DSDT address is < 4G.
> +          //
> +          Buffer64 = AcpiTableInstance->Fadt3->Dsdt;
>          } else {
>            AcpiTableInstance->Fadt3->Dsdt = 0;
>            Buffer64 = (UINT64) (UINTN) AcpiTableInstance->Dsdt3;
>