[PATCH 7/8] x86/amd-iommu: Panic if IOMMU command buffer reset fails

[Joerg Roedel <joerg.roedel@amd.com>]

To prevent the driver from doing recursive command buffer
resets, just panic when that recursion happens.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 arch/x86/include/asm/amd_iommu_types.h |    3 +++
 arch/x86/kernel/amd_iommu.c            |    7 +++++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/amd_iommu_types.h b/arch/x86/include/asm/amd_iommu_types.h
index c54bc97..e676746 100644
--- a/arch/x86/include/asm/amd_iommu_types.h
+++ b/arch/x86/include/asm/amd_iommu_types.h
@@ -337,6 +337,9 @@ struct amd_iommu {
 	/* if one, we need to send a completion wait command */
 	bool need_sync;
 
+	/* becomes true if a command buffer reset is running */
+	bool reset_in_progress;
+
 	/* default dma_ops domain for that IOMMU */
 	struct dma_ops_domain *default_dom;
 };
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 2333d61..b62a2f6 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -553,9 +553,16 @@ static void reset_iommu_command_buffer(struct amd_iommu *iommu)
 {
 	pr_err("AMD-Vi: Resetting IOMMU command buffer\n");
 
+	if (iommu->reset_in_progress)
+		panic("AMD-Vi: ILLEGAL_COMMAND_ERROR while resetting command buffer\n");
+
+	iommu->reset_in_progress = true;
+
 	amd_iommu_reset_cmd_buffer(iommu);
 	flush_all_devices_for_iommu(iommu);
 	flush_all_domains_on_iommu(iommu);
+
+	iommu->reset_in_progress = false;
 }
 
 /****************************************************************************
-- 
1.6.3.3