[PATCH 13/22] iommu/vt-d: Identify domains using first level page table

[Lu Baolu]

This checks whether a domain should use the first level page
table for map/unmap and marks it in the domain structure.

Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 39 +++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 34723f6be672..71ad5e5feae2 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -307,6 +307,14 @@ static int hw_pass_through = 1;
  */
 #define DOMAIN_FLAG_LOSE_CHILDREN              BIT(1)
 
+/*
+ * When VT-d works in the scalable mode, it allows DMA translation to
+ * happen through either first level or second level page table. This
+ * bit marks that the DMA translation for the domain goes through the
+ * first level page table, otherwise, it goes through the second level.
+ */
+#define DOMAIN_FLAG_USE_FIRST_LEVEL            BIT(2)
+
 #define for_each_domain_iommu(idx, domain)                     \
        for (idx = 0; idx < g_num_of_iommus; idx++)             \
                if (domain->iommu_refcnt[idx])
@@ -1714,6 +1722,35 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
 #endif
 }
 
+/*
+ * Check and return whether first level is used by default for
+ * DMA translation. Currently, we make it off by setting
+ * first_level_support = 0, and will change it to -1 after all
+ * map/unmap paths support first level page table.
+ */
+static bool first_level_by_default(void)
+{
+       struct dmar_drhd_unit *drhd;
+       struct intel_iommu *iommu;
+       static int first_level_support = 0;
+
+       if (likely(first_level_support != -1))
+               return first_level_support;
+
+       first_level_support = 1;
+
+       rcu_read_lock();
+       for_each_active_iommu(iommu, drhd) {
+               if (!sm_supported(iommu) || !ecap_flts(iommu->ecap)) {
+                       first_level_support = 0;
+                       break;
+               }
+       }
+       rcu_read_unlock();
+
+       return first_level_support;
+}
+
 static struct dmar_domain *alloc_domain(int flags)
 {
        struct dmar_domain *domain;
@@ -1725,6 +1762,8 @@ static struct dmar_domain *alloc_domain(int flags)
        memset(domain, 0, sizeof(*domain));
        domain->nid = NUMA_NO_NODE;
        domain->flags = flags;
+       if (first_level_by_default())
+               domain->flags |= DOMAIN_FLAG_USE_FIRST_LEVEL;
        domain->has_iotlb_device = false;
        INIT_LIST_HEAD(&domain->devices);
 
-- 
2.17.1

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