From c06b53e52e7a14c68aec347c5305d217a34b414f Mon Sep 17 00:00:00 2001
From: Johannes Schlatow <johannes.schlatow@genode-labs.com>
Date: Wed, 15 Nov 2023 14:39:56 +0100
Subject: [PATCH] acpi_drv: add config for ignoring DMAR table

By not evaluating the DMAR table, we disable the IOMMU.

genodelabs/genode#5002
---
 repos/os/src/drivers/acpi/README  |  9 +++++++++
 repos/os/src/drivers/acpi/acpi.cc |  8 ++++++--
 repos/os/src/drivers/acpi/acpi.h  |  3 ++-
 repos/os/src/drivers/acpi/main.cc | 12 +++++++-----
 4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/repos/os/src/drivers/acpi/README b/repos/os/src/drivers/acpi/README
index a82319f469..504677b9a1 100644
--- a/repos/os/src/drivers/acpi/README
+++ b/repos/os/src/drivers/acpi/README
@@ -33,3 +33,12 @@ Usage
 !
 !<start name="platform_drv">
 !  ...
+
+Config
+------
+
+This server also reports available DMA remapping units (IOMMU) as specified in
+the 'DMAR' table. In order to disable the IOMMU, you may provide the following
+config:
+
+! <config ignore_drhd="yes"/>
diff --git a/repos/os/src/drivers/acpi/acpi.cc b/repos/os/src/drivers/acpi/acpi.cc
index 05166147d5..9c64b3bb8a 100644
--- a/repos/os/src/drivers/acpi/acpi.cc
+++ b/repos/os/src/drivers/acpi/acpi.cc
@@ -1611,7 +1611,8 @@ static void attribute_hex(Xml_generator &xml, char const *name,
 }
 
 
-void Acpi::generate_report(Genode::Env &env, Genode::Allocator &alloc)
+void Acpi::generate_report(Genode::Env &env, Genode::Allocator &alloc,
+                           Xml_node const &config_xml)
 {
 	/* parse table */
 	Acpi_table acpi_table(env, alloc);
@@ -1667,11 +1668,14 @@ void Acpi::generate_report(Genode::Env &env, Genode::Allocator &alloc)
 			});
 		};
 
+		bool ignore_drhd = config_xml.attribute_value("ignore_drhd", false);
 		for (Dmar_entry *entry = Dmar_entry::list()->first();
 		     entry; entry = entry->next()) {
 
 			entry->apply([&] (Dmar_common const &dmar) {
-				if (dmar.read<Dmar_common::Type>() == Dmar_common::Type::DRHD) {
+				if (!ignore_drhd &&
+				    dmar.read<Dmar_common::Type>() == Dmar_common::Type::DRHD)
+				{
 					Dmar_drhd drhd(dmar.base());
 
 					size_t size_log2 = drhd.read<Dmar_drhd::Size::Num_pages>() + 12;
diff --git a/repos/os/src/drivers/acpi/acpi.h b/repos/os/src/drivers/acpi/acpi.h
index 04a862664a..ecdeb439fe 100644
--- a/repos/os/src/drivers/acpi/acpi.h
+++ b/repos/os/src/drivers/acpi/acpi.h
@@ -17,6 +17,7 @@
 /* Genode includes */
 #include <base/env.h>
 #include <base/allocator.h>
+#include <util/xml_node.h>
 
 
 namespace Acpi
@@ -24,7 +25,7 @@ namespace Acpi
 	/**
 	 * Generate report rom
 	 */
-	void generate_report(Genode::Env&, Genode::Allocator&);
+	void generate_report(Genode::Env&, Genode::Allocator&, Genode::Xml_node const&);
 }
 
 #endif /* _ACPI_H_ */
diff --git a/repos/os/src/drivers/acpi/main.cc b/repos/os/src/drivers/acpi/main.cc
index 2daa9d6868..27dcdc8b65 100644
--- a/repos/os/src/drivers/acpi/main.cc
+++ b/repos/os/src/drivers/acpi/main.cc
@@ -15,6 +15,7 @@
 #include <base/component.h>
 #include <base/heap.h>
 #include <base/log.h>
+#include <base/attached_rom_dataspace.h>
 #include <util/xml_generator.h>
 
 /* local includes */
@@ -30,15 +31,16 @@ namespace Acpi {
 
 struct Acpi::Main
 {
-	Genode::Env &_env;
-	Genode::Heap _heap { _env.ram(), _env.rm() };
+	Genode::Env           &_env;
+	Genode::Heap           _heap { _env.ram(), _env.rm() };
+	Attached_rom_dataspace _config { _env, "config" };
 
 	struct Acpi_reporter
 	{
-		Acpi_reporter(Env &env, Heap &heap)
+		Acpi_reporter(Env &env, Heap &heap, Xml_node const &config_xml)
 		{
 			try {
-				Acpi::generate_report(env, heap);
+				Acpi::generate_report(env, heap, config_xml);
 			} catch (Genode::Xml_generator::Buffer_exceeded) {
 				error("ACPI report too large - failure");
 				throw;
@@ -49,7 +51,7 @@ struct Acpi::Main
 		}
 	};
 
-	Acpi_reporter         _acpi_reporter { _env, _heap };
+	Acpi_reporter         _acpi_reporter { _env, _heap, _config.xml() };
 	Smbios_table_reporter _smbt_reporter { _env, _heap };
 
 	Main(Env &env) : _env(env) { }