[PATCH v8 7/8] genirq/msi: map/unmap the MSI doorbells on msi_domain_alloc/free_irqs

[Eric Auger]

This patch handles the iommu mapping of MSI doorbells that require to
be mapped in an iommu domain. This happens on msi_domain_alloc/free_irqs
since this is called in code that can sleep (pci_enable/disable_msi):
iommu_map/unmap is not stated as atomic. On msi_domain_(de)activate and
msi_domain_set_affinity, which must be atomic, we just lookup for this
pre-allocated/mapped IOVA.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>

---
v7 -> v8:
- new percpu pointer type
- exit from the irq domain hierarchy parsing on first map/unmap success
- reset desc->irq to 0 on mapping failure

v7: creation
---
 kernel/irq/msi.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 79 insertions(+), 8 deletions(-)

diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 72bf4d6..d5f95e6 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -14,6 +14,8 @@
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/msi.h>
+#include <linux/msi-iommu.h>
+#include <linux/iommu.h>
 
 /* Temparory solution for building, will be removed later */
 #include <linux/pci.h>
@@ -322,6 +324,56 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
 }
 
 /**
+ * msi_handle_doorbell_mappings: in case the irq data corresponds to an
+ * MSI that requires iommu mapping, traverse the irq domain hierarchy
+ * to retrieve the doorbells to handle and iommu_map/unmap them according
+ * to @map boolean.
+ *
+ * @data: irq data handle
+ * @map: mapping if true, unmapping if false
+ */
+static int msi_handle_doorbell_mappings(struct irq_data *data, bool map)
+{
+	for (; data; data = data->parent_data) {
+		struct device *dev =
+			msi_desc_to_dev(irq_data_get_msi_desc(data));
+		struct irq_chip *chip = irq_data_get_irq_chip(data);
+		const struct irq_chip_msi_doorbell_info *dbinfo;
+		struct iommu_domain *domain;
+		phys_addr_t __percpu *db_addr;
+		dma_addr_t iova;
+		int ret = 0, i;
+
+		domain = iommu_msi_domain(dev);
+		if (!domain)
+			continue;
+
+		if (!chip->msi_doorbell_info)
+			continue;
+
+		dbinfo = chip->msi_doorbell_info(data);
+		if (!dbinfo)
+			return -EINVAL;
+
+		for (i = 0; i < dbinfo->nb_doorbells; i++) {
+			db_addr = per_cpu_ptr(dbinfo->percpu_doorbells, i);
+			if (map) {
+				ret = iommu_msi_get_doorbell_iova(domain,
+								  *db_addr,
+								  dbinfo->size,
+								  dbinfo->prot,
+								  &iova);
+				if (ret)
+					return ret;
+			} else
+				iommu_msi_put_doorbell_iova(domain, *db_addr);
+		}
+		break;
+	}
+	return 0;
+}
+
+/**
  * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
  * @domain:	The domain to allocate from
  * @dev:	Pointer to device struct of the device for which the interrupts
@@ -352,17 +404,26 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 
 		virq = __irq_domain_alloc_irqs(domain, virq, desc->nvec_used,
 					       dev_to_node(dev), &arg, false);
-		if (virq < 0) {
-			ret = -ENOSPC;
-			if (ops->handle_error)
-				ret = ops->handle_error(domain, desc, ret);
-			if (ops->msi_finish)
-				ops->msi_finish(&arg, ret);
-			return ret;
-		}
+		if (virq < 0)
+			goto error;
 
 		for (i = 0; i < desc->nvec_used; i++)
 			irq_set_msi_desc_off(virq, i, desc);
+
+		for (i = 0; i < desc->nvec_used; i++) {
+			ret = msi_handle_doorbell_mappings(
+				irq_get_irq_data(virq + i), true);
+			if (ret)
+				break;
+		}
+		if (ret) {
+			for (; i >= 0; i--)
+				msi_handle_doorbell_mappings(
+					irq_get_irq_data(virq + i), false);
+			irq_domain_free_irqs(virq, desc->nvec_used);
+			desc->irq = 0;
+			goto error;
+		}
 	}
 
 	if (ops->msi_finish)
@@ -377,6 +438,13 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 	}
 
 	return 0;
+error:
+	ret = -ENOSPC;
+	if (ops->handle_error)
+		ret = ops->handle_error(domain, desc, ret);
+	if (ops->msi_finish)
+		ops->msi_finish(&arg, ret);
+	return ret;
 }
 
 /**
@@ -396,6 +464,9 @@ void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
 		 * entry. If that's the case, don't do anything.
 		 */
 		if (desc->irq) {
+			msi_handle_doorbell_mappings(
+				irq_get_irq_data(desc->irq),
+				false);
 			irq_domain_free_irqs(desc->irq, desc->nvec_used);
 			desc->irq = 0;
 		}
-- 
1.9.1