[PATCH v2 08/14] iommu/riscv: Prepare info->domain for concurrent RCU read access

[Andrew Jones]

An upcoming compose_msi_msg() implementation reads info->domain from
potentially atomic context, concurrent with domain switches. Apply
RCU in preparation.

Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
---
 drivers/iommu/riscv/iommu.c | 14 ++++++++------
 drivers/iommu/riscv/iommu.h |  3 ++-
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index bfe606a0cb9a..27dfd60834ac 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -1241,6 +1241,8 @@ static void riscv_iommu_free_paging_domain(struct iommu_domain *iommu_domain)
 
 	WARN_ON(!list_empty(&domain->bonds));
 
+	synchronize_rcu();
+
 	riscv_iommu_ir_free_paging_domain(iommu_domain);
 
 	if ((int)domain->pscid > 0)
@@ -1296,8 +1298,8 @@ static int riscv_iommu_attach_paging_domain(struct iommu_domain *iommu_domain,
 	}
 
 	riscv_iommu_iodir_update(iommu, dev, fsc, ta);
-	riscv_iommu_bond_unlink(info->domain, dev);
-	info->domain = domain;
+	riscv_iommu_bond_unlink(rcu_access_pointer(info->domain), dev);
+	rcu_assign_pointer(info->domain, domain);
 
 	return 0;
 }
@@ -1373,8 +1375,8 @@ static int riscv_iommu_attach_blocking_domain(struct iommu_domain *iommu_domain,
 
 	/* Make device context invalid, translation requests will fault w/ #258 */
 	riscv_iommu_iodir_update(iommu, dev, RISCV_IOMMU_FSC_BARE, 0);
-	riscv_iommu_bond_unlink(info->domain, dev);
-	info->domain = NULL;
+	riscv_iommu_bond_unlink(rcu_access_pointer(info->domain), dev);
+	rcu_assign_pointer(info->domain, NULL);
 
 	return 0;
 }
@@ -1394,8 +1396,8 @@ static int riscv_iommu_attach_identity_domain(struct iommu_domain *iommu_domain,
 	struct riscv_iommu_info *info = dev_iommu_priv_get(dev);
 
 	riscv_iommu_iodir_update(iommu, dev, RISCV_IOMMU_FSC_BARE, RISCV_IOMMU_PC_TA_V);
-	riscv_iommu_bond_unlink(info->domain, dev);
-	info->domain = NULL;
+	riscv_iommu_bond_unlink(rcu_access_pointer(info->domain), dev);
+	rcu_assign_pointer(info->domain, NULL);
 
 	return 0;
 }
diff --git a/drivers/iommu/riscv/iommu.h b/drivers/iommu/riscv/iommu.h
index 5d83537911b6..ded18aec8010 100644
--- a/drivers/iommu/riscv/iommu.h
+++ b/drivers/iommu/riscv/iommu.h
@@ -15,6 +15,7 @@
 #include <linux/types.h>
 #include <linux/iopoll.h>
 #include <linux/irqdomain.h>
+#include <linux/rcupdate.h>
 #include <linux/generic_pt/iommu.h>
 
 #include "iommu-bits.h"
@@ -33,7 +34,7 @@ PT_IOMMU_CHECK_DOMAIN(struct riscv_iommu_domain, riscvpt.iommu, domain);
 
 /* Private IOMMU data for managed devices, dev_iommu_priv_* */
 struct riscv_iommu_info {
-	struct riscv_iommu_domain *domain;
+	struct riscv_iommu_domain __rcu *domain;
 	struct irq_domain *irqdomain;
 };
 
-- 
2.43.0