[RFC v1 3/8] intel/vt-d: make DMAR table parsing code more flexible

[Wei Liu <wei.liu@xxxxxxxxxx>]

Microsoft Hypervisor provides a set of hypercalls to manage device
domains. The root kernel should parse the DMAR so that it can program
the IOMMU (with hypercalls) correctly.

The DMAR code was designed to work with Intel IOMMU only. Add two more
parameters to make it useful to Microsoft Hypervisor. Microsoft
Hypervisor does not need the DMAR parsing code to allocate an Intel
IOMMU structure; it also wishes to always reparse the DMAR table even
after it has been parsed before.

Adjust Intel IOMMU code to use the new dmar_table_init. There should be
no functional change to Intel IOMMU code.

Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
---
We may be able to combine alloc and force_parse?
---
 drivers/iommu/intel/dmar.c          | 38 ++++++++++++++++++++---------
 drivers/iommu/intel/iommu.c         |  2 +-
 drivers/iommu/intel/irq_remapping.c |  2 +-
 include/linux/dmar.h                |  2 +-
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 84057cb9596c..bd72f47c728b 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -408,7 +408,8 @@ dmar_find_dmaru(struct acpi_dmar_hardware_unit *drhd)
  * structure which uniquely represent one DMA remapping hardware unit
  * present in the platform
  */
-static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
+static int dmar_parse_one_drhd_internal(struct acpi_dmar_header *header,
+		void *arg, bool alloc)
 {
 	struct acpi_dmar_hardware_unit *drhd;
 	struct dmar_drhd_unit *dmaru;
@@ -440,12 +441,14 @@ static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
 		return -ENOMEM;
 	}
 
-	ret = alloc_iommu(dmaru);
-	if (ret) {
-		dmar_free_dev_scope(&dmaru->devices,
-				    &dmaru->devices_cnt);
-		kfree(dmaru);
-		return ret;
+	if (alloc) {
+		ret = alloc_iommu(dmaru);
+		if (ret) {
+			dmar_free_dev_scope(&dmaru->devices,
+					    &dmaru->devices_cnt);
+			kfree(dmaru);
+			return ret;
+		}
 	}
 	dmar_register_drhd_unit(dmaru);
 
@@ -456,6 +459,16 @@ static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
 	return 0;
 }
 
+static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
+{
+	return dmar_parse_one_drhd_internal(header, arg, true);
+}
+
+int dmar_parse_one_drhd_noalloc(struct acpi_dmar_header *header, void *arg)
+{
+	return dmar_parse_one_drhd_internal(header, arg, false);
+}
+
 static void dmar_free_drhd(struct dmar_drhd_unit *dmaru)
 {
 	if (dmaru->devices && dmaru->devices_cnt)
@@ -633,7 +646,7 @@ static inline int dmar_walk_dmar_table(struct acpi_table_dmar *dmar,
  * parse_dmar_table - parses the DMA reporting table
  */
 static int __init
-parse_dmar_table(void)
+parse_dmar_table(bool alloc)
 {
 	struct acpi_table_dmar *dmar;
 	int drhd_count = 0;
@@ -650,6 +663,9 @@ parse_dmar_table(void)
 		.cb[ACPI_DMAR_TYPE_SATC] = &dmar_parse_one_satc,
 	};
 
+	if (!alloc)
+		cb.cb[ACPI_DMAR_TYPE_HARDWARE_UNIT] = &dmar_parse_one_drhd_noalloc;
+
 	/*
 	 * Do it again, earlier dmar_tbl mapping could be mapped with
 	 * fixed map.
@@ -840,13 +856,13 @@ void __init dmar_register_bus_notifier(void)
 }
 
 
-int __init dmar_table_init(void)
+int __init dmar_table_init(bool alloc, bool force_parse)
 {
 	static int dmar_table_initialized;
 	int ret;
 
-	if (dmar_table_initialized == 0) {
-		ret = parse_dmar_table();
+	if (dmar_table_initialized == 0 || force_parse) {
+		ret = parse_dmar_table(alloc);
 		if (ret < 0) {
 			if (ret != -ENODEV)
 				pr_info("Parse DMAR table failure.\n");
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index be35284a2016..a4294d310b93 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4310,7 +4310,7 @@ int __init intel_iommu_init(void)
 	}
 
 	down_write(&dmar_global_lock);
-	if (dmar_table_init()) {
+	if (dmar_table_init(true, false)) {
 		if (force_on)
 			panic("tboot: Failed to initialize DMAR table\n");
 		goto out_free_dmar;
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index f912fe45bea2..0e8abef862e4 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -732,7 +732,7 @@ static int __init intel_prepare_irq_remapping(void)
 		return -ENODEV;
 	}
 
-	if (dmar_table_init() < 0)
+	if (dmar_table_init(true, false) < 0)
 		return -ENODEV;
 
 	if (intel_cap_audit(CAP_AUDIT_STATIC_IRQR, NULL))
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index e04436a7ff27..f88535d41a6e 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -106,7 +106,7 @@ static inline bool dmar_rcu_check(void)
 	for_each_dev_scope((devs), (cnt), (i), (tmp))			\
 		if (!(tmp)) { continue; } else
 
-extern int dmar_table_init(void);
+extern int dmar_table_init(bool alloc, bool force_parse);
 extern int dmar_dev_scope_init(void);
 extern void dmar_register_bus_notifier(void);
 extern int dmar_parse_dev_scope(void *start, void *end, int *cnt,
-- 
2.30.2