iommm/vt-d: Store irq domain in struct device

As a first step to make X86 utilize the direct MSI irq domain operations
store the irq domain pointer in the device struct when a device is probed.

This is done from dmar_pci_bus_add_dev() because it has to work even when
DMA remapping is disabled. It only overrides the irqdomain of devices which
are handled by a regular PCI/MSI irq domain which protects PCI devices
behind special busses like VMD which have their own irq domain.

No functional change. It just avoids the redirection through
arch_*_msi_irqs() and allows the PCI/MSI core to directly invoke the irq
domain alloc/free functions instead of having to look up the irq domain for
every single MSI interupt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200826112333.714566121@linutronix.de

drivers/iommu/intel/dmar.c

@@ -316,6 +316,9 @@ static int dmar_pci_bus_add_dev(struct dmar_pci_notify_info *info)
 	if (ret < 0 && dmar_dev_scope_status == 0)
 		dmar_dev_scope_status = ret;
 
+	if (ret >= 0)
+		intel_irq_remap_add_device(info);
+
 	return ret;
 }
 

drivers/iommu/intel/irq_remapping.c

@@ -1092,6 +1092,22 @@ static int reenable_irq_remapping(int eim)
 	return -1;
 }
 
+/*
+ * Store the MSI remapping domain pointer in the device if enabled.
+ *
+ * This is called from dmar_pci_bus_add_dev() so it works even when DMA
+ * remapping is disabled. Only update the pointer if the device is not
+ * already handled by a non default PCI/MSI interrupt domain. This protects
+ * e.g. VMD devices.
+ */
+void intel_irq_remap_add_device(struct dmar_pci_notify_info *info)
+{
+	if (!irq_remapping_enabled || pci_dev_has_special_msi_domain(info->dev))
+		return;
+
+	dev_set_msi_domain(&info->dev->dev, map_dev_to_ir(info->dev));
+}
+
 static void prepare_irte(struct irte *irte, int vector, unsigned int dest)
 {
 	memset(irte, 0, sizeof(*irte));

include/linux/intel-iommu.h

@@ -425,6 +425,8 @@ struct q_inval {
 	int             free_cnt;
 };
 
+struct dmar_pci_notify_info;
+
 #ifdef CONFIG_IRQ_REMAP
 /* 1MB - maximum possible interrupt remapping table size */
 #define INTR_REMAP_PAGE_ORDER	8
@@ -439,6 +441,11 @@ struct ir_table {
 	struct irte *base;
 	unsigned long *bitmap;
 };
+
+void intel_irq_remap_add_device(struct dmar_pci_notify_info *info);
+#else
+static inline void
+intel_irq_remap_add_device(struct dmar_pci_notify_info *info) { }
 #endif
 
 struct iommu_flush {