[PATCH] iommu/amd: Track when amd_iommu_v2 init is complete

[Oded Gabbay <oded.gabbay@amd.com>]

This patch adds a new exported function to amd_iommu_v2, which returns 1 if the
amd_iommu_v2 initialization function has completed, and 0 otherwise.

This is necessary for the case when amd_iommu_v2 is compiled inside the kernel
image (not as module) and another module (e.g. amdkfd), which is also compiled
inside the kernel image, is dependent on amd_iommu_v2 functionality.

In that case, there is no mechanism in the kernel that enforces the order of
loading between the two modules. Therefore, If the amd_iommu_v2 is loaded
_after_ the other module, and the other module calls one of
amd_iommu_v2 exported functions _before_ amd_iommu_v2 is loaded, than that
function will fail, and as a result, the calling module may fail as well.

Note that when the two modules are compiled as modules, this situation can't
occur as the kernel enforces the order of loading.

Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
---
 drivers/iommu/amd_iommu_v2.c | 11 +++++++++++
 include/linux/amd-iommu.h    |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 1e6360e..2456f18 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -895,6 +895,14 @@ out_unlock:
 }
 EXPORT_SYMBOL(amd_iommu_set_invalidate_ctx_cb);
 
+static int iommu_v2_init_completed;
+
+int amd_iommu_v2_is_init_completed(void)
+{
+	return iommu_v2_init_completed;
+}
+EXPORT_SYMBOL(amd_iommu_v2_is_init_completed);
+
 static int __init amd_iommu_v2_init(void)
 {
 	int ret;
@@ -903,6 +911,7 @@ static int __init amd_iommu_v2_init(void)
 
 	if (!amd_iommu_v2_supported()) {
 		pr_info("AMD IOMMUv2 functionality not available on this system\n");
+		iommu_v2_init_completed = 1;
 		/*
 		 * Load anyway to provide the symbols to other modules
 		 * which may use AMD IOMMUv2 optionally.
@@ -919,6 +928,8 @@ static int __init amd_iommu_v2_init(void)
 
 	amd_iommu_register_ppr_notifier(&ppr_nb);
 
+	iommu_v2_init_completed = 1;
+
 	return 0;
 
 out:
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 2b08e79..115c03a 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -169,6 +169,8 @@ typedef void (*amd_iommu_invalidate_ctx)(struct pci_dev *pdev, int pasid);
 extern int amd_iommu_set_invalidate_ctx_cb(struct pci_dev *pdev,
 					   amd_iommu_invalidate_ctx cb);
 
+extern int amd_iommu_v2_is_init_completed(void);
+
 #else
 
 static inline int amd_iommu_detect(void) { return -ENODEV; }
-- 
2.1.0