[RFC PATCH 03/13] iommu/intel: zap context table entries on kexec

[James Gowans <jgowans@amazon.com>]

Instead of fully shutting down the IOMMU on kexec, rather zap context
table entries for devices. This is the initial step to be able to
persist some domains. Once a struct iommu_domain can be marked
persistent then those persistent domains will be skipped when doing the
IOMMU shut down.
---
 drivers/iommu/intel/dmar.c  |  1 +
 drivers/iommu/intel/iommu.c | 34 ++++++++++++++++++++++++++++++----
 drivers/iommu/intel/iommu.h |  2 ++
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 1c8d3141cb55..f79aba382e77 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1099,6 +1099,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 	spin_lock_init(&iommu->device_rbtree_lock);
 	mutex_init(&iommu->iopf_lock);
 	iommu->node = NUMA_NO_NODE;
+	INIT_LIST_HEAD(&iommu->domains);
 
 	ver = readl(iommu->reg + DMAR_VER_REG);
 	pr_info("%s: reg_base_addr %llx ver %d:%d cap %llx ecap %llx\n",
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 9ff8b83c19a3..2297cbb0253f 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1575,6 +1575,7 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
 		goto err_clear;
 	}
 	domain_update_iommu_cap(domain);
+	list_add(&domain->domains, &iommu->domains);
 
 	spin_unlock(&iommu->lock);
 	return 0;
@@ -3185,6 +3186,33 @@ static void intel_disable_iommus(void)
 		iommu_disable_translation(iommu);
 }
 
+static void zap_context_table_entries(struct intel_iommu *iommu)
+{
+	struct context_entry *context;
+	struct dmar_domain *domain;
+	struct device_domain_info *device;
+	int bus, devfn;
+	u16 did_old;
+
+	list_for_each_entry(domain, &iommu->domains, domains) {
+		list_for_each_entry(device, &domain->devices, link) {
+			context = iommu_context_addr(iommu, device->bus, device->devfn, 0);
+			if (!context || !context_present(context))
+				continue;
+			context_domain_id(context);
+			context_clear_entry(context);
+			__iommu_flush_cache(iommu, context, sizeof(*context));
+			iommu->flush.flush_context(iommu,
+						   did_old,
+						   (((u16)bus) << 8) | devfn,
+						   DMA_CCMD_MASK_NOBIT,
+						   DMA_CCMD_DEVICE_INVL);
+			iommu->flush.flush_iotlb(iommu,	did_old, 0, 0,
+						 DMA_TLB_DSI_FLUSH);
+		}
+	}
+}
+
 void intel_iommu_shutdown(void)
 {
 	struct dmar_drhd_unit *drhd;
@@ -3197,10 +3225,8 @@ void intel_iommu_shutdown(void)
 
 	/* Disable PMRs explicitly here. */
 	for_each_iommu(iommu, drhd)
-		iommu_disable_protect_mem_regions(iommu);
-
-	/* Make sure the IOMMUs are switched off */
-	intel_disable_iommus();
+		zap_context_table_entries(iommu);
+	return
 
 	up_write(&dmar_global_lock);
 }
diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index b67c14da1240..cfd006588824 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -606,6 +606,7 @@ struct dmar_domain {
 	spinlock_t lock;		/* Protect device tracking lists */
 	struct list_head devices;	/* all devices' list */
 	struct list_head dev_pasids;	/* all attached pasids */
+	struct list_head domains;	/* all struct dmar_domains on this IOMMU */
 
 	spinlock_t cache_lock;		/* Protect the cache tag list */
 	struct list_head cache_tags;	/* Cache tag list */
@@ -749,6 +750,7 @@ struct intel_iommu {
 	void *perf_statistic;
 
 	struct iommu_pmu *pmu;
+	struct list_head domains;	/* all struct dmar_domains on this IOMMU */
 };
 
 /* PCI domain-device relationship */
-- 
2.34.1