AMD/IOMMU: Don't opencode memcpy() in queue_iommu_command()

In practice, this allows the compiler to replace the loop with a pair of movs.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Brian Woods <brian.woods@amd.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

xen/drivers/passthrough/amd/iommu_cmd.c

@@ -24,8 +24,7 @@
 
 static int queue_iommu_command(struct amd_iommu *iommu, u32 cmd[])
 {
-    u32 tail, head, *cmd_buffer;
-    int i;
+    uint32_t tail, head;
 
     tail = iommu->cmd_buffer.tail;
     if ( ++tail == iommu->cmd_buffer.entries )
@@ -35,12 +34,9 @@ static int queue_iommu_command(struct amd_iommu *iommu, u32 cmd[])
                                       IOMMU_CMD_BUFFER_HEAD_OFFSET));
     if ( head != tail )
     {
-        cmd_buffer = (u32 *)(iommu->cmd_buffer.buffer +
-                             (iommu->cmd_buffer.tail *
-                             IOMMU_CMD_BUFFER_ENTRY_SIZE));
-
-        for ( i = 0; i < IOMMU_CMD_BUFFER_U32_PER_ENTRY; i++ )
-            cmd_buffer[i] = cmd[i];
+        memcpy(iommu->cmd_buffer.buffer +
+               (iommu->cmd_buffer.tail * IOMMU_CMD_BUFFER_ENTRY_SIZE),
+               cmd, IOMMU_CMD_BUFFER_ENTRY_SIZE);
 
         iommu->cmd_buffer.tail = tail;
         return 1;

xen/include/asm-x86/hvm/svm/amd-iommu-defs.h

@@ -187,7 +187,6 @@
 
 #define IOMMU_CMD_BUFFER_ENTRY_SIZE			16
 #define IOMMU_CMD_BUFFER_POWER_OF2_ENTRIES_PER_PAGE	8
-#define IOMMU_CMD_BUFFER_U32_PER_ENTRY 	(IOMMU_CMD_BUFFER_ENTRY_SIZE / 4)
 
 #define IOMMU_CMD_OPCODE_MASK			0xF0000000
 #define IOMMU_CMD_OPCODE_SHIFT			28