[PATCH v2 1/1] iommu/vt-d: Use device numa domain if RHSA is missing

[Lu Baolu]

If there are multiple NUMA domains but the RHSA is missing in ACPI/DMAR
table, we could default to the device NUMA domain as fall back. This could
also benefit a vIOMMU use case where only single vIOMMU is exposed, hence
no RHSA will be present but device numa domain can be correct.

Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/iommu.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

Change log:
v1->v2:
  - Add a comment as suggested by Kevin.
    https://lore.kernel.org/linux-iommu/MWHPR11MB1645E6D6BD1EFDFA139AA37C8C520@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 7f844d1c8cd9..69d5a87188f4 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -698,12 +698,47 @@ static int domain_update_iommu_superpage(struct dmar_domain *domain,
 	return fls(mask);
 }
 
+static int domain_update_device_node(struct dmar_domain *domain)
+{
+	struct device_domain_info *info;
+	int nid = NUMA_NO_NODE;
+
+	assert_spin_locked(&device_domain_lock);
+
+	if (list_empty(&domain->devices))
+		return NUMA_NO_NODE;
+
+	list_for_each_entry(info, &domain->devices, link) {
+		if (!info->dev)
+			continue;
+
+		/*
+		 * There could possibly be multiple device numa nodes as devices
+		 * within the same domain may sit behind different IOMMUs. There
+		 * isn't perfect answer in such situation, so we select first
+		 * come first served policy.
+		 */
+		nid = dev_to_node(info->dev);
+		if (nid != NUMA_NO_NODE)
+			break;
+	}
+
+	return nid;
+}
+
 /* Some capabilities may be different across iommus */
 static void domain_update_iommu_cap(struct dmar_domain *domain)
 {
 	domain_update_iommu_coherency(domain);
 	domain->iommu_snooping = domain_update_iommu_snooping(NULL);
 	domain->iommu_superpage = domain_update_iommu_superpage(domain, NULL);
+
+	/*
+	 * If RHSA is missing, we should default to the device numa domain
+	 * as fall back.
+	 */
+	if (domain->nid == NUMA_NO_NODE)
+		domain->nid = domain_update_device_node(domain);
 }
 
 struct context_entry *iommu_context_addr(struct intel_iommu *iommu, u8 bus,
@@ -5096,8 +5131,6 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
 		if (type == IOMMU_DOMAIN_DMA)
 			intel_init_iova_domain(dmar_domain);
 
-		domain_update_iommu_cap(dmar_domain);
-
 		domain = &dmar_domain->domain;
 		domain->geometry.aperture_start = 0;
 		domain->geometry.aperture_end   =
-- 
2.17.1