[RFCv1,1/7] genirq/msi: Allow preset IOVA in struct msi_desc for MSI doorbell address

Commit Message

Nicolin Chen Nov. 9, 2024, 5:48 a.m. UTC

Currently, the IOVA and its mapping (to physical doorbell address) is done
by the dma-iommu via the iommu_cookie in the struct msi_desc, which is the
structure used by three parties: genirq, irqchip and dma-iommu.

However, when dealing with a nested translation on ARM64, the MSI doorbell
address is behind the SMMU (IOMMU on ARM64), thus HW needs to be programed
with the stage-1 IOVA, i.e. guest-level IOVA, rather than asking dma-iommu
to allocate one.

To support a guest-programmable pathway, first we need to make sure struct
msi_desc will allow a preset IOVA v.s. using iommu_cookie. Add an msi_iova
to the structure and init its value to PHYS_ADDR_MAX. And provide a helper
for drivers to get the msi_iova out of an msi_desc object.

A following patch will change msi_setup_msi_descs and msix_setup_msi_descs
to call msi_domain_insert_msi_desc and finish the actual value forwarding.

Signed-off-by: Nicolin Chen <[e-mail]>
---
 include/linux/msi.h | 11 +++++++++++
 kernel/irq/msi.c    |  6 ++++++
 2 files changed, 17 insertions(+)

Patch

diff --git a/include/linux/msi.h b/include/linux/msi.h
index b10093c4d00e..873094743065 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -185,6 +185,7 @@  struct msi_desc {
 	struct irq_affinity_desc	*affinity;
 #ifdef CONFIG_IRQ_MSI_IOMMU
 	const void			*iommu_cookie;
+	dma_addr_t			msi_iova;
 #endif
 #ifdef CONFIG_SYSFS
 	struct device_attribute		*sysfs_attrs;
@@ -296,6 +297,11 @@  static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
 {
 	desc->iommu_cookie = iommu_cookie;
 }
+
+static inline dma_addr_t msi_desc_get_iova(struct msi_desc *desc)
+{
+	return desc->msi_iova;
+}
 #else
 static inline const void *msi_desc_get_iommu_cookie(struct msi_desc *desc)
 {
@@ -306,6 +312,11 @@  static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
 					     const void *iommu_cookie)
 {
 }
+
+static inline dma_addr_t msi_desc_get_iova(struct msi_desc *desc)
+{
+	return PHYS_ADDR_MAX;
+}
 #endif
 
 int msi_domain_insert_msi_desc(struct device *dev, unsigned int domid,
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 3a24d6b5f559..f3159ec0f036 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -81,6 +81,9 @@  static struct msi_desc *msi_alloc_desc(struct device *dev, int nvec,
 
 	desc->dev = dev;
 	desc->nvec_used = nvec;
+#ifdef CONFIG_IRQ_MSI_IOMMU
+	desc->msi_iova = PHYS_ADDR_MAX;
+#endif
 	if (affinity) {
 		desc->affinity = kmemdup_array(affinity, nvec, sizeof(*desc->affinity), GFP_KERNEL);
 		if (!desc->affinity) {
@@ -158,6 +161,9 @@  int msi_domain_insert_msi_desc(struct device *dev, unsigned int domid,
 
 	/* Copy type specific data to the new descriptor. */
 	desc->pci = init_desc->pci;
+#ifdef CONFIG_IRQ_MSI_IOMMU
+	desc->msi_iova = init_desc->msi_iova;
+#endif
 
 	return msi_insert_desc(dev, desc, domid, init_desc->msi_index);
 }