[PATCH RFCv2 01/13] genirq/msi: Store the IOMMU IOVA directly in msi_desc instead of iommu_cookie

[Nicolin Chen]

From: Jason Gunthorpe <jgg@xxxxxxxxxx>

All the iommu cases simply want to override the MSI page's address with
the IOVA that was mapped through the iommu. This doesn't need a cookie
pointer, we just need to store the IOVA and its page size in the msi_desc.

Instead provide msi_desc_set_iommu_msi_iova() which allows the IOMMU side
to specify the IOVA that the MSI page is placed during
iommu_dma_prepare(). This is stored in the msi_desc and then
iommu_dma_compose_msi_msg() is a simple inline that sets address_hi/lo.

The next patch will correct the naming.

This is done because we cannot correctly lock access to group->domain in
the atomic context that iommu_dma_compose_msi_msg() is called under. Today
the locking miss is tolerable because dma_iommu.c operates under an
assumption that the domain does not change while a driver is probed.

However iommufd now permits the domain to change while the driver is
probed and VFIO userspace can create races with IRQ changes calling
iommu_dma_prepare/compose_msi_msg() and changing/freeing the iommu_domain.

Removing the pointer, and critically, the call to
iommu_get_domain_for_dev() during compose resolves this race.

Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 include/linux/iommu.h     |  6 ------
 include/linux/msi.h       | 45 +++++++++++++++++++++++----------------
 drivers/iommu/dma-iommu.c | 30 +++++---------------------
 3 files changed, 32 insertions(+), 49 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 318d27841130..3a4215966c1b 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1513,7 +1513,6 @@ static inline void iommu_debugfs_setup(void) {}
 int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
 
 int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr);
-void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg);
 
 #else /* CONFIG_IOMMU_DMA */
 
@@ -1529,11 +1528,6 @@ static inline int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_a
 {
 	return 0;
 }
-
-static inline void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
-{
-}
-
 #endif	/* CONFIG_IOMMU_DMA */
 
 /*
diff --git a/include/linux/msi.h b/include/linux/msi.h
index b10093c4d00e..d442b4a69d56 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -184,7 +184,8 @@ struct msi_desc {
 	struct msi_msg			msg;
 	struct irq_affinity_desc	*affinity;
 #ifdef CONFIG_IRQ_MSI_IOMMU
-	const void			*iommu_cookie;
+	u64				iommu_msi_iova : 58;
+	u64				iommu_msi_page_shift : 6;
 #endif
 #ifdef CONFIG_SYSFS
 	struct device_attribute		*sysfs_attrs;
@@ -285,28 +286,36 @@ struct msi_desc *msi_next_desc(struct device *dev, unsigned int domid,
 
 #define msi_desc_to_dev(desc)		((desc)->dev)
 
-#ifdef CONFIG_IRQ_MSI_IOMMU
-static inline const void *msi_desc_get_iommu_cookie(struct msi_desc *desc)
-{
-	return desc->iommu_cookie;
-}
-
-static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
-					     const void *iommu_cookie)
+static inline void msi_desc_set_iommu_msi_iova(struct msi_desc *desc,
+					       u64 msi_iova,
+					       unsigned int page_shift)
 {
-	desc->iommu_cookie = iommu_cookie;
-}
-#else
-static inline const void *msi_desc_get_iommu_cookie(struct msi_desc *desc)
-{
-	return NULL;
+#ifdef CONFIG_IRQ_MSI_IOMMU
+	desc->iommu_msi_iova = msi_iova >> page_shift;
+	desc->iommu_msi_page_shift = page_shift;
+#endif
 }
 
-static inline void msi_desc_set_iommu_cookie(struct msi_desc *desc,
-					     const void *iommu_cookie)
+/**
+ * iommu_dma_compose_msi_msg() - Apply translation to an MSI message
+ * @desc: MSI descriptor prepared by iommu_dma_prepare_msi()
+ * @msg: MSI message containing target physical address
+ */
+static inline void iommu_dma_compose_msi_msg(struct msi_desc *desc,
+					     struct msi_msg *msg)
 {
-}
+#ifdef CONFIG_IRQ_MSI_IOMMU
+	if (desc->iommu_msi_page_shift) {
+		u64 msi_iova = desc->iommu_msi_iova
+			       << desc->iommu_msi_page_shift;
+
+		msg->address_hi = upper_32_bits(msi_iova);
+		msg->address_lo = lower_32_bits(msi_iova) |
+				  (msg->address_lo &
+				   ((1 << desc->iommu_msi_page_shift) - 1));
+	}
 #endif
+}
 
 int msi_domain_insert_msi_desc(struct device *dev, unsigned int domid,
 			       struct msi_desc *init_desc);
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 2a9fa0c8cc00..bf91e014d179 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1815,7 +1815,7 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
 	static DEFINE_MUTEX(msi_prepare_lock); /* see below */
 
 	if (!domain || !domain->iova_cookie) {
-		desc->iommu_cookie = NULL;
+		msi_desc_set_iommu_msi_iova(desc, 0, 0);
 		return 0;
 	}
 
@@ -1827,33 +1827,13 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
 	mutex_lock(&msi_prepare_lock);
 	msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
 	mutex_unlock(&msi_prepare_lock);
-
-	msi_desc_set_iommu_cookie(desc, msi_page);
-
 	if (!msi_page)
 		return -ENOMEM;
-	return 0;
-}
 
-/**
- * iommu_dma_compose_msi_msg() - Apply translation to an MSI message
- * @desc: MSI descriptor prepared by iommu_dma_prepare_msi()
- * @msg: MSI message containing target physical address
- */
-void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
-{
-	struct device *dev = msi_desc_to_dev(desc);
-	const struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
-	const struct iommu_dma_msi_page *msi_page;
-
-	msi_page = msi_desc_get_iommu_cookie(desc);
-
-	if (!domain || !domain->iova_cookie || WARN_ON(!msi_page))
-		return;
-
-	msg->address_hi = upper_32_bits(msi_page->iova);
-	msg->address_lo &= cookie_msi_granule(domain->iova_cookie) - 1;
-	msg->address_lo += lower_32_bits(msi_page->iova);
+	msi_desc_set_iommu_msi_iova(
+		desc, msi_page->iova,
+		ilog2(cookie_msi_granule(domain->iova_cookie)));
+	return 0;
 }
 
 static int iommu_dma_init(void)
-- 
2.43.0