@@ -31,6 +31,7 @@ dt_irq_xlate_func dt_irq_xlate;
struct dt_device_node *dt_host;
/* Interrupt controller node*/
const struct dt_device_node *dt_interrupt_controller;
+rwlock_t dt_host_lock;
/**
* struct dt_alias_prop - Alias property in 'aliases' node
@@ -2137,7 +2138,11 @@ int unflatten_device_tree(const void *fdt, struct dt_device_node **mynodes)
dt_dprintk(" <- unflatten_device_tree()\n");
+ /* Init r/w lock for host device tree. */
+ rwlock_init(&dt_host_lock);
+
return 0;
+
}
static void dt_alias_add(struct dt_alias_prop *ap,
@@ -114,6 +114,8 @@ int iommu_release_dt_devices(struct domain *d)
if ( !is_iommu_enabled(d) )
return 0;
+ read_lock(&dt_host_lock);
+
list_for_each_entry_safe(dev, _dev, &hd->dt_devices, domain_list)
{
rc = iommu_deassign_dt_device(d, dev);
@@ -121,10 +123,14 @@ int iommu_release_dt_devices(struct domain *d)
{
dprintk(XENLOG_ERR, "Failed to deassign %s in domain %u\n",
dt_node_full_name(dev), d->domain_id);
+
+ read_unlock(&dt_host_lock);
return rc;
}
}
+ read_unlock(&dt_host_lock);
+
return 0;
}
@@ -251,6 +257,8 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
int ret;
struct dt_device_node *dev;
+ read_lock(&dt_host_lock);
+
switch ( domctl->cmd )
{
case XEN_DOMCTL_assign_device:
@@ -304,7 +312,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
spin_unlock(&dtdevs_lock);
if ( d == dom_io )
+ {
+ read_unlock(&dt_host_lock);
return -EINVAL;
+ }
ret = iommu_add_dt_device(dev);
if ( ret < 0 )
@@ -342,7 +353,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
break;
if ( d == dom_io )
+ {
+ read_unlock(&dt_host_lock);
return -EINVAL;
+ }
ret = iommu_deassign_dt_device(d, dev);
@@ -357,5 +371,6 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
break;
}
+ read_unlock(&dt_host_lock);
return ret;
}
@@ -18,6 +18,7 @@
#include <xen/string.h>
#include <xen/types.h>
#include <xen/list.h>
+#include <xen/rwlock.h>
#define DEVICE_TREE_MAX_DEPTH 16
@@ -216,6 +217,11 @@ extern struct dt_device_node *dt_host;
*/
extern const struct dt_device_node *dt_interrupt_controller;
+/*
+ * Lock that protects r/w updates to unflattened device tree i.e. dt_host.
+ */
+extern rwlock_t dt_host_lock;
+
/**
* Find the interrupt controller
* For the moment we handle only one interrupt controller: the first
Dynamic programming ops will modify the dt_host and there might be other function which are browsing the dt_host at the same time. To avoid the race conditions, adding rwlock for browsing the dt_host during runtime. dt_host writer will be added in the follow-up patch titled "xen/arm: Implement device tree node addition functionalities." Reason behind adding rwlock instead of spinlock: For now, dynamic programming is the sole modifier of dt_host in Xen during run time. All other access functions like iommu_release_dt_device() are just reading the dt_host during run-time. So, there is a need to protect others from browsing the dt_host while dynamic programming is modifying it. rwlock is better suitable for this task as spinlock won't be able to differentiate between read and write access. Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com> --- Changes from v7: Keep one lock for dt_host instead of lock for each node under dt_host. --- --- xen/common/device_tree.c | 5 +++++ xen/drivers/passthrough/device_tree.c | 15 +++++++++++++++ xen/include/xen/device_tree.h | 6 ++++++ 3 files changed, 26 insertions(+)