[PATCH v4 01/14] swiotlb: Remove external access to io_tlb_start

[Claire Chang]

Add a new function, get_swiotlb_start(), and remove external access to
io_tlb_start, so we can entirely hide struct swiotlb inside of swiotlb.c
in the following patches.

Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
---
 arch/powerpc/platforms/pseries/svm.c | 4 ++--
 drivers/xen/swiotlb-xen.c            | 4 ++--
 include/linux/swiotlb.h              | 1 +
 kernel/dma/swiotlb.c                 | 5 +++++
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
index 7b739cc7a8a9..c10c51d49f3d 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -55,8 +55,8 @@ void __init svm_swiotlb_init(void)
 	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, false))
 		return;
 
-	if (io_tlb_start)
-		memblock_free_early(io_tlb_start,
+	if (vstart)
+		memblock_free_early(vstart,
 				    PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
 	panic("SVM: Cannot allocate SWIOTLB buffer");
 }
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 2b385c1b4a99..91f8c68d1a9b 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -192,8 +192,8 @@ int __ref xen_swiotlb_init(int verbose, bool early)
 	/*
 	 * IO TLB memory already allocated. Just use it.
 	 */
-	if (io_tlb_start != 0) {
-		xen_io_tlb_start = phys_to_virt(io_tlb_start);
+	if (is_swiotlb_active()) {
+		xen_io_tlb_start = phys_to_virt(get_swiotlb_start());
 		goto end;
 	}
 
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index d9c9fc9ca5d2..83200f3b042a 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -81,6 +81,7 @@ void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
 bool is_swiotlb_active(void);
+phys_addr_t get_swiotlb_start(void);
 void __init swiotlb_adjust_size(unsigned long new_size);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 7c42df6e6100..e180211f6ad9 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -719,6 +719,11 @@ bool is_swiotlb_active(void)
 	return io_tlb_end != 0;
 }
 
+phys_addr_t get_swiotlb_start(void)
+{
+	return io_tlb_start;
+}
+
 #ifdef CONFIG_DEBUG_FS
 
 static int __init swiotlb_create_debugfs(void)
--

This can be dropped if Christoph's swiotlb cleanups are landed.
https://lore.kernel.org/linux-iommu/20210207160934.2955931-1-hch@xxxxxx/T/#m7124f29b6076d462101fcff6433295157621da09 

2.30.0.478.g8a0d178c01-goog