3 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/include/asm/amd_iommu_types.h b/arch/x86/include/asm/amd_iommu_types.h
index 5e46e78f3b1b..86a0ff0aeac7 100644
--- a/arch/x86/include/asm/amd_iommu_types.h
+++ b/arch/x86/include/asm/amd_iommu_types.h
@@ -141,6 +141,7 @@
 
 /* constants to configure the command buffer */
 #define CMD_BUFFER_SIZE    8192
+#define CMD_BUFFER_UNINITIALIZED 1
 #define CMD_BUFFER_ENTRIES 512
 #define MMIO_CMD_SIZE_SHIFT 56
 #define MMIO_CMD_SIZE_512 (0x9ULL << MMIO_CMD_SIZE_SHIFT)
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index b06f29e275e9..71dfc0af8e50 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -392,6 +392,7 @@ static int __iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
         u32 tail, head;
         u8 *target;
 
+        WARN_ON(iommu->cmd_buf_size & CMD_BUFFER_UNINITIALIZED);
         tail = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
         target = iommu->cmd_buf + tail;
         memcpy_toio(target, cmd, sizeof(*cmd));
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 8975965f3e67..5edf41c7127c 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -438,7 +438,7 @@ static u8 * __init alloc_command_buffer(struct amd_iommu *iommu)
         if (cmd_buf == NULL)
                 return NULL;
 
-        iommu->cmd_buf_size = CMD_BUFFER_SIZE;
+        iommu->cmd_buf_size = CMD_BUFFER_SIZE | CMD_BUFFER_UNINITIALIZED;
 
         return cmd_buf;
 }
@@ -474,12 +474,13 @@ static void iommu_enable_command_buffer(struct amd_iommu *iommu)
                     &entry, sizeof(entry));
 
         amd_iommu_reset_cmd_buffer(iommu);
+        iommu->cmd_buf_size &= ~(CMD_BUFFER_UNINITIALIZED);
 }
 
 static void __init free_command_buffer(struct amd_iommu *iommu)
 {
         free_pages((unsigned long)iommu->cmd_buf,
-                   get_order(iommu->cmd_buf_size));
+                   get_order(iommu->cmd_buf_size & ~(CMD_BUFFER_UNINITIALIZED)));
 }
 
 /* allocates the memory where the IOMMU will log its events to */