[RFC PATCH 4/4] dma-mapping: Add API to preserve/restore DMA allocation

[Samiullah Khawaja]

Add new DMA APIs that allow preserving/restoring DMA allocations across
live update.

Signed-off-by: Samiullah Khawaja <skhawaja at google.com>
---
 include/linux/dma-mapping.h | 50 +++++++++++++++++++++++++++++++++++
 kernel/dma/mapping.c        | 52 +++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index db8ab24a54f4..3756fc15467b 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -210,6 +210,15 @@ void *dma_vmap_noncontiguous(struct device *dev, size_t size,
 void dma_vunmap_noncontiguous(struct device *dev, void *vaddr);
 int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
 		size_t size, struct sg_table *sgt);
+#ifdef CONFIG_DMA_LIVEUPDATE
+int dma_preserve_allocation_attrs(struct device *dev, void *cpu_addr,
+				  size_t size, dma_addr_t dma_handle,
+				  unsigned long attrs, u64 *state);
+void dma_unpreserve_allocation(struct device *dev, u64 state);
+void *dma_restore_allocation_attrs(struct device *dev, size_t size,
+				   dma_addr_t *dma_handle, gfp_t gfp,
+				   unsigned long attrs, u64 state);
+#endif
 #else /* CONFIG_HAS_DMA */
 static inline dma_addr_t dma_map_page_attrs(struct device *dev,
 		struct page *page, size_t offset, size_t size,
@@ -496,6 +505,26 @@ static inline bool dma_need_unmap(struct device *dev)
 }
 #endif /* !CONFIG_HAS_DMA || !CONFIG_DMA_NEED_SYNC */
 
+#if !defined(CONFIG_DMA_LIVEUPDATE) || !defined(CONFIG_HAS_DMA)
+static inline int dma_preserve_allocation_attrs(struct device *dev, void *cpu_addr,
+						size_t size, dma_addr_t dma_handle,
+						unsigned long attrs, u64 *state)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void dma_unpreserve_allocation(struct device *dev, u64 state)
+{
+}
+
+static inline void *dma_restore_allocation_attrs(struct device *dev, size_t size,
+						 dma_addr_t *dma_handle, gfp_t gfp,
+						 unsigned long attrs, u64 state)
+{
+	return NULL;
+}
+#endif
+
 struct page *dma_alloc_pages(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp);
 void dma_free_pages(struct device *dev, size_t size, struct page *page,
@@ -618,6 +647,27 @@ static inline void *dma_alloc_coherent(struct device *dev, size_t size,
 			(gfp & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0);
 }
 
+static inline int dma_preserve_coherent_allocation(struct device *dev, void *cpu_addr,
+						   size_t size, dma_addr_t dma_handle, u64 *state)
+{
+	return dma_preserve_allocation_attrs(dev, cpu_addr, size,
+					     dma_handle, 0, state);
+}
+
+static inline void dma_unpreserve_coherent_allocation(struct device *dev, u64 state)
+{
+	dma_unpreserve_allocation(dev, state);
+}
+
+static inline void *dma_restore_coherent_allocation(struct device *dev, size_t size,
+						    dma_addr_t *dma_handle,
+						    gfp_t gfp, u64 state)
+{
+	return dma_restore_allocation_attrs(dev, size, dma_handle, gfp,
+					    (gfp & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0,
+					    state);
+}
+
 static inline void dma_free_coherent(struct device *dev, size_t size,
 		void *cpu_addr, dma_addr_t dma_handle)
 {
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 23ed8eb9233e..c315b74a0884 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -12,6 +12,8 @@
 #include <linux/gfp.h>
 #include <linux/iommu-dma.h>
 #include <linux/kmsan.h>
+#include <linux/kexec_handover.h>
+#include <linux/kho/abi/dma_alloc.h>
 #include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
@@ -628,6 +630,56 @@ u64 dma_get_required_mask(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dma_get_required_mask);
 
+#ifdef CONFIG_DMA_LIVEUPDATE
+int dma_preserve_allocation_attrs(struct device *dev, void *cpu_addr,
+				  size_t size, dma_addr_t dma_handle,
+				  unsigned long attrs, u64 *state)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+#ifdef CONFIG_DMA_DECLARE_COHERENT
+	return -EOPNOTSUPP;
+#endif
+
+	if (dma_alloc_direct(dev, ops))
+		return dma_direct_preserve_allocation(dev, cpu_addr, size,
+						      dma_handle, attrs,
+						      state);
+
+	return -EOPNOTSUPP;
+}
+EXPORT_SYMBOL(dma_preserve_allocation_attrs);
+
+void dma_unpreserve_allocation(struct device *dev, u64 state)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (dma_alloc_direct(dev, ops))
+		dma_direct_unpreserve_allocation(dev, state);
+}
+EXPORT_SYMBOL(dma_unpreserve_allocation);
+
+void *dma_restore_allocation_attrs(struct device *dev, size_t size,
+				   dma_addr_t *dma_handle, gfp_t gfp,
+				   unsigned long attrs, u64 state)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	WARN_ON_ONCE(!dev->coherent_dma_mask);
+
+#ifdef CONFIG_DMA_DECLARE_COHERENT
+	return NULL;
+#endif
+
+	if (dma_alloc_direct(dev, ops))
+		return dma_direct_restore_allocation(dev, size, dma_handle,
+						     gfp, attrs, state);
+
+	return NULL;
+}
+EXPORT_SYMBOL(dma_restore_allocation_attrs);
+#endif
+
 void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp_t flag, unsigned long attrs)
 {
-- 
2.54.0.545.g6539524ca2-goog