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

James Gowans
2024-09-16T11:32:35Z

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