buildroot/boot/edk2/0001-OvmfPkg-QemuVideoDxe-add-feature-PCD-to-remap-frameb.patch

From 921c78f57a16b00debd58899a48e7045015c374b Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Mon, 17 Jun 2024 17:07:41 +0200
Subject: [PATCH] OvmfPkg/QemuVideoDxe: add feature PCD to remap framebuffer
 W/C

Some platforms (such as SBSA-QEMU on recent builds of the emulator) only
tolerate misaligned accesses to normal memory, and raise alignment
faults on such accesses to device memory, which is the default for PCIe
MMIO BARs.

When emulating a PCIe graphics controller, the framebuffer is typically
exposed via a MMIO BAR, while the disposition of the region is closer to
memory (no side effects on reads or writes, except for the changing
picture on the screen; direct random access to any pixel in the image).

In order to permit the use of such controllers on platforms that only
tolerate these types of accesses for normal memory, it is necessary to
remap the memory. Use the DXE services to set the desired capabilities
and attributes.

Hide this behavior under a feature PCD so only platforms that really
need it can enable it. (OVMF on x86 has no need for this)

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Upstream: https://github.com/tianocore/edk2/commit/c1d1910be6e04a8b1a73090cf2881fb698947a6e
Signed-off-by: Romain Naour <romain.naour@smile.fr>
---
 OvmfPkg/OvmfPkg.dec                   |  5 +++++
 OvmfPkg/QemuVideoDxe/Gop.c            | 19 +++++++++++++++++++
 OvmfPkg/QemuVideoDxe/Qemu.h           |  2 +-
 OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf |  4 ++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 51be9a5959..2c40de8a13 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -444,3 +444,8 @@
 
   ## This feature flag indicates the firmware build supports secure boot.
   gUefiOvmfPkgTokenSpaceGuid.PcdSecureBootSupported|FALSE|BOOLEAN|0x6d
+
+  ## Whether QemuVideoDxe should perform a EFI_MEMORY_WC remap of the PCI
+  #  framebuffer. This might be required on platforms that do not tolerate
+  #  misaligned accesses otherwise.
+  gUefiOvmfPkgTokenSpaceGuid.PcdRemapFrameBufferWriteCombine|FALSE|BOOLEAN|0x75
diff --git a/OvmfPkg/QemuVideoDxe/Gop.c b/OvmfPkg/QemuVideoDxe/Gop.c
index b11eed7558..a29c025afd 100644
--- a/OvmfPkg/QemuVideoDxe/Gop.c
+++ b/OvmfPkg/QemuVideoDxe/Gop.c
@@ -9,6 +9,8 @@
 
 #include "Qemu.h"
 
+#include <Library/DxeServicesTableLib.h>
+
 STATIC
 VOID
 QemuVideoCompleteModeInfo (
@@ -54,6 +56,7 @@ QemuVideoCompleteModeData (
   EFI_GRAPHICS_OUTPUT_MODE_INFORMATION  *Info;
   EFI_ACPI_ADDRESS_SPACE_DESCRIPTOR     *FrameBufDesc;
   QEMU_VIDEO_MODE_DATA                  *ModeData;
+  EFI_STATUS                            Status;
 
   ModeData = &Private->ModeData[Mode->Mode];
   Info     = Mode->Info;
@@ -79,6 +82,22 @@ QemuVideoCompleteModeData (
     (UINT64)Mode->FrameBufferSize
     ));
 
+  if (FeaturePcdGet (PcdRemapFrameBufferWriteCombine)) {
+    Status = gDS->SetMemorySpaceCapabilities (
+                    FrameBufDesc->AddrRangeMin,
+                    FrameBufDesc->AddrLen,
+                    EFI_MEMORY_UC | EFI_MEMORY_WC | EFI_MEMORY_XP
+                    );
+    ASSERT_EFI_ERROR (Status);
+
+    Status = gDS->SetMemorySpaceAttributes (
+                    FrameBufDesc->AddrRangeMin,
+                    FrameBufDesc->AddrLen,
+                    EFI_MEMORY_WC | EFI_MEMORY_XP
+                    );
+    ASSERT_EFI_ERROR (Status);
+  }
+
   FreePool (FrameBufDesc);
   return EFI_SUCCESS;
 }
diff --git a/OvmfPkg/QemuVideoDxe/Qemu.h b/OvmfPkg/QemuVideoDxe/Qemu.h
index 57341a0bbf..a3da725fbf 100644
--- a/OvmfPkg/QemuVideoDxe/Qemu.h
+++ b/OvmfPkg/QemuVideoDxe/Qemu.h
@@ -13,7 +13,7 @@
 #ifndef _QEMU_H_
 #define _QEMU_H_
 
-#include <Uefi.h>
+#include <PiDxe.h>
 #include <Protocol/GraphicsOutput.h>
 #include <Protocol/PciIo.h>
 #include <Protocol/DriverSupportedEfiVersion.h>
diff --git a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
index 43a6e07faa..4c0870171b 100644
--- a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
+++ b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
@@ -44,6 +44,7 @@
 
 [LibraryClasses]
   BaseMemoryLib
+  DxeServicesTableLib
   FrameBufferBltLib
   DebugLib
   DevicePathLib
@@ -61,6 +62,9 @@
   gEfiDevicePathProtocolGuid                    # PROTOCOL BY_START
   gEfiPciIoProtocolGuid                         # PROTOCOL TO_START
 
+[FeaturePcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdRemapFrameBufferWriteCombine
+
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId
   gUefiOvmfPkgTokenSpaceGuid.PcdVideoResolutionSource
-- 
2.45.0