[PATCH 2/2] iommu/dmar: catch early fault occurrences

[Yuri Volchkov]

First dmar faults can happen even before linux have scanned PCI
bus. In such case worker will not have chance to lookup a
corresponding 'struct pci_dev'.

This commit defers processing of the fault until intel_iommu_init
function has been called. At this point of time pci devices will be
already initialized.

Signed-off-by: Yuri Volchkov <volch...@amazon.de>
---
 drivers/iommu/dmar.c        | 51 ++++++++++++++++++++++++++++++++++++-
 drivers/iommu/intel-iommu.c |  1 +
 include/linux/intel-iommu.h |  1 +
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 0749873e3e41..8db2af3de29f 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1674,7 +1674,10 @@ void dmar_msi_read(int irq, struct msi_msg *msg)
 }
 
 struct dmar_fault_info {
-       struct work_struct work;
+       union {
+               struct work_struct work;
+               struct list_head backlog_list;
+       };
        struct intel_iommu *iommu;
        int type;
        int pasid;
@@ -1757,12 +1760,58 @@ static int dmar_fault_handle_one(struct dmar_fault_info 
*info)
        return 0;
 }
 
+struct fault_backlog {
+       struct list_head queue;
+       struct mutex lock;
+       bool is_active;
+};
+
+static struct fault_backlog fault_backlog = {
+       .queue = LIST_HEAD_INIT(fault_backlog.queue),
+       .lock = __MUTEX_INITIALIZER(fault_backlog.lock),
+       .is_active = true,
+};
+
+void dmar_process_deferred_faults(void)
+{
+       struct dmar_fault_info *info, *tmp;
+
+       mutex_lock(&fault_backlog.lock);
+       WARN_ON(!fault_backlog.is_active);
+
+       list_for_each_entry_safe(info, tmp, &fault_backlog.queue,
+                                backlog_list) {
+               dmar_fault_handle_one(info);
+               list_del(&info->backlog_list);
+               free_dmar_fault_info(info);
+       }
+       fault_backlog.is_active = false;
+       mutex_unlock(&fault_backlog.lock);
+}
+
 static void dmar_fault_handle_work(struct work_struct *work)
 {
        struct dmar_fault_info *info;
 
        info = container_of(work, struct dmar_fault_info, work);
 
+       if (fault_backlog.is_active) {
+               /* Postpone handling until PCI devices will be
+                * initialized
+                */
+
+               mutex_lock(&fault_backlog.lock);
+               if (!fault_backlog.is_active) {
+                       mutex_unlock(&fault_backlog.lock);
+                       goto process;
+               }
+
+               list_add(&info->backlog_list, &fault_backlog.queue);
+               mutex_unlock(&fault_backlog.lock);
+               return;
+       }
+
+process:
        dmar_fault_handle_one(info);
        free_dmar_fault_info(info);
 }
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 3f974919d3bd..a97c05fac5e9 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5041,6 +5041,7 @@ int __init intel_iommu_init(void)
                iommu_disable_protect_mem_regions(iommu);
        }
        pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
+       dmar_process_deferred_faults();
 
        intel_iommu_enabled = 1;
        intel_iommu_debugfs_init();
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index f8963c833fb0..480a31b41263 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -649,6 +649,7 @@ extern void qi_flush_dev_iotlb(struct intel_iommu *iommu, 
u16 sid, u16 pfsid,
 extern int qi_submit_sync(struct qi_desc *desc, struct intel_iommu *iommu);
 
 extern int dmar_ir_support(void);
+extern void dmar_process_deferred_faults(void);
 
 void *alloc_pgtable_page(int node);
 void free_pgtable_page(void *vaddr);
-- 
2.23.0




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