[RFC 20/26] memory: Add wrappers of intermediate steps for read/write

[Zhao Liu <zhao1.liu@intel.com>]

Add these 2 wrappers to allow bindgen to generate the bindings based on
MemoryRegionSection:
 * section_rust_write_continue_step()
 * section_rust_read_continue_step()

Then Rust side could be able to re-build a full write/read processes as
address_space_write()/address_space_read_full() did.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 include/system/memory.h | 51 +++++++++++++++++++++++++++++++++++++++++
 system/physmem.c        | 16 +++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/include/system/memory.h b/include/system/memory.h
index 110ad0a3b590..a75c8c348f58 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -3413,6 +3413,57 @@ uint8_t *section_get_host_addr(const MemoryRegionSection *section,
 void section_fuzz_dma_read(MemoryRegionSection *section,
                            hwaddr addr, hwaddr len);
 
+/**
+ * section_rust_write_continue_step: write to #MemoryRegionSection.
+ *
+ * Not: This function should only used by Rust side, and user shouldn't
+ * call it directly!
+ *
+ * This function provides a wrapper of flatview_write_continue_step(),
+ * and allows Rust side to re-build a full write process as
+ * address_space_write() did.
+ *
+ * Should be called from an RCU critical section.
+ *
+ * @section: #MemoryRegionSection to be accessed.
+ * @attrs: memory transaction attributes.
+ * @buf: buffer with the data to be written.
+ * @len: the number of bytes to write.
+ * @mr_addr: address within that memory region.
+ * @l: the actual length of the data is written after function returns.
+ *
+ * Return a MemTxResult indicating whether the operation succeeded
+ * or failed (eg unassigned memory, device rejected the transaction,
+ * IOMMU fault).
+ */
+MemTxResult section_rust_write_continue_step(MemoryRegionSection *section,
+    MemTxAttrs attrs, const uint8_t *buf, hwaddr len, hwaddr mr_addr, hwaddr *l);
+
+/**
+ * section_read_continue_step: read from #MemoryRegionSection.
+ *
+ * Not: This function should only used by Rust side, and user shouldn't
+ * call it directly!
+ *
+ * This function provides a wrapper of flatview_read_continue_step(),
+ * and allows Rust side to re-build a full write process as
+ * address_space_read_full() did.
+ *
+ * Should be called from an RCU critical section.
+ *
+ * @section: #MemoryRegionSection to be accessed.
+ * @attrs: memory transaction attributes.
+ * @buf: buffer to be written.
+ * @len: the number of bytes is expected to read.
+ * @mr_addr: address within that memory region.
+ * @l: the actual length of the data is read after function returns.
+ *
+ * Return a MemTxResult indicating whether the operation succeeded
+ * or failed.
+ */
+MemTxResult section_read_continue_step(MemoryRegionSection *section,
+    MemTxAttrs attrs, uint8_t *buf, hwaddr len, hwaddr mr_addr, hwaddr *l);
+
 /*
  * Inhibit technologies that require discarding of pages in RAM blocks, e.g.,
  * to manage the actual amount of memory consumed by the VM (then, the memory
diff --git a/system/physmem.c b/system/physmem.c
index e06633f4d8a2..0c30dea775ca 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -3119,6 +3119,14 @@ static MemTxResult flatview_read_continue_step(MemTxAttrs attrs, uint8_t *buf,
     }
 }
 
+MemTxResult
+section_read_continue_step(MemoryRegionSection *section, MemTxAttrs attrs,
+                           uint8_t *buf, hwaddr len, hwaddr mr_addr,
+                           hwaddr *l)
+{
+    return flatview_read_continue_step(attrs, buf, len, mr_addr, l, section->mr);
+}
+
 /* Called within RCU critical section.  */
 MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
                                    MemTxAttrs attrs, void *ptr,
@@ -3707,6 +3715,14 @@ static MemTxResult address_space_write_continue_cached(MemTxAttrs attrs,
     return result;
 }
 
+MemTxResult
+section_rust_write_continue_step(MemoryRegionSection *section, MemTxAttrs attrs,
+                                 const uint8_t *buf, hwaddr len, hwaddr mr_addr,
+                                 hwaddr *l)
+{
+    return flatview_write_continue_step(attrs, buf, len, mr_addr, l, section->mr);
+}
+
 /* Called within RCU critical section.  */
 static MemTxResult address_space_read_continue_cached(MemTxAttrs attrs,
                                                       void *ptr, hwaddr len,
-- 
2.34.1