If multiple devices are being passed through to the same domain and they
share a single SMMU, then they only require a single iommu_domain.
In arm_smmu_assign_dev, before a new iommu_domain is created, the
xen_domain->contexts is checked for any iommu_domains that are already
assigned to device that uses the same SMMU as the current device. If one
is found, attach the device to that iommu_domain. If a new one isn't
found, create a new iommu_domain just like before.
The arm_smmu_deassign_dev function assumes that there is a single
device per iommu_domain. This meant that when the first device was
deassigned, the iommu_domain was freed and when another device was
deassigned a crash occurred in xen.
To fix this, a reference counter was added to the iommu_domain struct.
When an arm_smmu_xen_device references an iommu_domain, the
iommu_domains ref is incremented. When that reference is removed, the
iommu_domains ref is decremented. The iommu_domain will only be freed
when the ref is 0.
Signed-off-by: Robbie VanVossen
Reviewed-by: Julien Grall
---
Changed since v3:
* Fixed formatting
Changed since v2:
* Fixed coding style
* Removed an unnecessary error message
* Added some helper functions to clean up the workflow in arm_smmu_assign_dev
a bit
Changed since v1:
* Fixed coding style for comments
* Move increment/decrement outside of attach/detach functions
* Expanded xen_domain->lock to protect more of the assign/deassign
functions
* Removed iommu_domain add/remove_device functions
---
xen/drivers/passthrough/arm/smmu.c | 99 ++--
1 file changed, 71 insertions(+), 28 deletions(-)
diff --git a/xen/drivers/passthrough/arm/smmu.c
b/xen/drivers/passthrough/arm/smmu.c
index a7a7da9..8a9b58b 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -223,6 +223,7 @@ struct iommu_domain
/* Runtime SMMU configuration for this iommu_domain */
struct arm_smmu_domain *priv;
+ atomic_t ref;
/* Used to link iommu_domain contexts for a same domain.
* There is at least one per-SMMU to used by the domain.
* */
@@ -2564,12 +2565,45 @@ static void arm_smmu_iotlb_flush(struct domain *d,
unsigned long gfn,
arm_smmu_iotlb_flush_all(d);
}
+static struct iommu_domain *arm_smmu_get_domain(struct domain *d,
+ struct device *dev)
+{
+ struct iommu_domain *domain;
+ struct arm_smmu_xen_domain *xen_domain;
+ struct arm_smmu_device *smmu;
+
+ xen_domain = domain_hvm_iommu(d)->arch.priv;
+
+ smmu = find_smmu_for_device(dev);
+ if (!smmu)
+ return NULL;
+
+ /*
+* Loop through the &xen_domain->contexts to locate a context
+* assigned to this SMMU
+*/
+ list_for_each_entry(domain, &xen_domain->contexts, list) {
+ if (domain->priv->smmu == smmu)
+ return domain;
+ }
+
+ return NULL;
+
+}
+
+static void arm_smmu_destroy_iommu_domain(struct iommu_domain *domain)
+{
+ list_del(&domain->list);
+ arm_smmu_domain_destroy(domain);
+ xfree(domain);
+}
+
static int arm_smmu_assign_dev(struct domain *d, u8 devfn,
struct device *dev)
{
struct iommu_domain *domain;
struct arm_smmu_xen_domain *xen_domain;
- int ret;
+ int ret = 0;
xen_domain = domain_hvm_iommu(d)->arch.priv;
@@ -2585,36 +2619,44 @@ static int arm_smmu_assign_dev(struct domain *d, u8
devfn,
return ret;
}
+ spin_lock(&xen_domain->lock);
+
/*
-* TODO: Share the context bank (i.e iommu_domain) when the device is
-* under the same SMMU as another device assigned to this domain.
-* Would it useful for PCI
+* Check to see if a context bank (iommu_domain) already exists for
+* this xen domain under the same SMMU
*/
- domain = xzalloc(struct iommu_domain);
- if (!domain)
- return -ENOMEM;
+ domain = arm_smmu_get_domain(d, dev);
+ if (!domain) {
- ret = arm_smmu_domain_init(domain);
- if (ret)
- goto err_dom_init;
+ domain = xzalloc(struct iommu_domain);
+ if (!domain) {
+ ret = -ENOMEM;
+ goto out;
+ }
- domain->priv->cfg.domain = d;
+ ret = arm_smmu_domain_init(domain);
+ if (ret) {
+ xfree(domain);
+ goto out;
+ }
- ret = arm_smmu_attach_dev(domain, dev);
- if (ret)
- goto err_attach_dev;
+ domain->priv->cfg.domain = d;
- spin_lock(&xen_domain->lock);
- /* Chain the new context to the domain */
- list_add(&domain->list, &xen_domain->contexts);
- spin_unlock(&xen_domain
