[PATCH v2 11/12] ArmVirtPkg/PlatformHasAcpiDtDxe: don't expose DT if QEMU provides ACPI

[Laszlo Ersek <lersek@redhat.com>]

This will let QEMU's "-no-acpi" option exclusively expose DT vs. ACPI to
the guest. Showing both is never needed (it is actually detrimental to the
adoption of standards, such as SBSA / SBBR).

* Without "-no-acpi", the firmware logs (from PlatformHasAcpiDtDxe)

> Found FwCfg @ 0x9020008/0x9020000
> Found FwCfg DMA @ 0x9020010
> InstallProtocolInterface: [EdkiiPlatformHasAcpiProtocol] 0

plus the usual messages. Later the guest kernel logs

> [    0.000000] efi:  SMBIOS 3.0=0x13bdb0000  ACPI 2.0=0x138440000

before it lists the ACPI tables one by one.

* With "-no-acpi", the firmware logs:

> PlatformHasAcpiDtDxe | Found FwCfg @ 0x9020008/0x9020000
> PlatformHasAcpiDtDxe | Found FwCfg DMA @ 0x9020010
> PlatformHasAcpiDtDxe | InstallProtocolInterface:
> PlatformHasAcpiDtDxe | [EdkiiPlatformHasDeviceTreeProtocol] 0
> FdtClientDxe         | OnPlatformHasDeviceTree: exposing DTB @
> FdtClientDxe         | 0x13FFBF000 to OS
> ...
> DXE_CORE             | Driver [AcpiTableDxe] was discovered but not
> DXE_CORE             | loaded!!
> DXE_CORE             | Driver [QemuFwCfgAcpiPlatform] was discovered but
> DXE_CORE             | not loaded!!
> ...
> RamDiskDxe           | RamDiskAcpiCheck: Cannot locate the EFI ACPI
> RamDiskDxe           | Table Protocol, unable to publish RAM disks to
> RamDiskDxe           | NFIT.

(BootGraphicsResourceTableDxe's ReadyToBoot callback --
InstallBootGraphicsResourceTable() -- handles the lack of
EFI_ACPI_TABLE_PROTOCOL silently.) Later the guest kernel logs

> [    0.000000] efi:  SMBIOS 3.0=0x13bdb0000  MEMATTR=0x138b3c018

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1430262
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.inf |  6 +--
 ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.c   | 45 ++++++++++++--------
 2 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.inf b/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.inf
index 7724cf215dda..95a56a10bb5c 100644
--- a/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.inf
+++ b/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.inf
@@ -28,11 +28,12 @@ [Packages]
   ArmPkg/ArmPkg.dec
   ArmVirtPkg/ArmVirtPkg.dec
   MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
   BaseLib
   DebugLib
-  PcdLib
+  QemuFwCfgLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
 
@@ -40,8 +41,5 @@ [Protocols]
   gEdkiiPlatformHasAcpiProtocolGuid       ## SOMETIMES_PRODUCES
   gEdkiiPlatformHasDeviceTreeProtocolGuid ## SOMETIMES_PRODUCES
 
-[FeaturePcd]
-  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot ## CONSUMES
-
 [Depex]
   TRUE
diff --git a/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.c b/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.c
index 8681f813a6b5..46f96401632c 100644
--- a/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.c
+++ b/ArmVirtPkg/PlatformHasAcpiDtDxe/PlatformHasAcpiDtDxe.c
@@ -15,7 +15,7 @@
 
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
-#include <Library/PcdLib.h>
+#include <Library/QemuFwCfgLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Protocol/PlatformHasAcpi.h>
 #include <Protocol/PlatformHasDeviceTree.h>
@@ -27,18 +27,27 @@ PlatformHasAcpiDt (
   IN EFI_SYSTEM_TABLE *SystemTable
   )
 {
-  EFI_STATUS Status;
-
-  Status = EFI_SUCCESS;
+  EFI_STATUS           Status;
+  FIRMWARE_CONFIG_ITEM FwCfgItem;
+  UINTN                FwCfgSize;
 
   //
   // If we fail to install any of the necessary protocols below, the OS will be
   // unbootable anyway (due to lacking hardware description), so tolerate no
   // errors here.
   //
-  // Always make ACPI available on 64-bit systems.
-  //
-  if (MAX_UINTN == MAX_UINT64) {
+  if (MAX_UINTN == MAX_UINT64 &&
+      !EFI_ERROR (
+         QemuFwCfgFindFile (
+           "etc/table-loader",
+           &FwCfgItem,
+           &FwCfgSize
+           )
+         )) {
+    //
+    // Only make ACPI available on 64-bit systems, and only if QEMU generates
+    // (a subset of) the ACPI tables.
+    //
     Status = gBS->InstallProtocolInterface (
                     &ImageHandle,
                     &gEdkiiPlatformHasAcpiProtocolGuid,
@@ -48,21 +57,21 @@ PlatformHasAcpiDt (
     if (EFI_ERROR (Status)) {
       goto Failed;
     }
+
+    return Status;
   }
 
   //
-  // Expose the Device Tree unless PcdPureAcpiBoot is set.
+  // Expose the Device Tree otherwise.
   //
-  if (!FeaturePcdGet (PcdPureAcpiBoot)) {
-    Status = gBS->InstallProtocolInterface (
-                    &ImageHandle,
-                    &gEdkiiPlatformHasDeviceTreeProtocolGuid,
-                    EFI_NATIVE_INTERFACE,
-                    NULL
-                    );
-    if (EFI_ERROR (Status)) {
-      goto Failed;
-    }
+  Status = gBS->InstallProtocolInterface (
+                  &ImageHandle,
+                  &gEdkiiPlatformHasDeviceTreeProtocolGuid,
+                  EFI_NATIVE_INTERFACE,
+                  NULL
+                  );
+  if (EFI_ERROR (Status)) {
+    goto Failed;
   }
 
   return Status;
-- 
2.9.3