x86/amd-iommu: warn when issuing command to uninitialized cmd buffer

To catch future potential issues we can add a warning whenever we issue
a command before the command buffer is fully initialized.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 1 insertions, 0 deletions

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));