Hi Vikram,
On 19/08/2023 01:28, Vikram Garhwal wrote:
Rename iommu_dt_device_is_assigned() to iommu_dt_device_is_assigned_locked().
Remove static type so this can also be used by SMMU drivers to check if the
device is being used before removing.
I have commented on v8. But I will comment here to make easier to keep
track of comment.
I don't think iommu_dt_device_is_assigned_locked() should be called from
the SMMU. If you want to check a device is assigned then it would be
best to use the internal state of the SMMU.
This has two benefits:
* This avoids what I view as a layer of violation
* This confirmed that the internal state match with what we expect
Moving spin_lock to caller was done to prevent the concurrent access to
iommu_dt_device_is_assigned while doing add/remove/assign/deassign. Follow-up
patches in this series introduces node add/remove feature.
Also, caller is required hold the correct lock so moved the function prototype
to a private header.
I don't understand how requiring the caller to hold the correct lock
means you need to move the protype in a private header. Can you clarify?
Signed-off-by: Vikram Garhwal <vikram.garh...@amd.com>
---
Changes from v7:
Update commit message.
Add ASSERT().
---
---
xen/drivers/passthrough/device_tree.c | 26 +++++++++++++++++++++----
xen/include/xen/iommu-private.h | 28 +++++++++++++++++++++++++++
2 files changed, 50 insertions(+), 4 deletions(-)
create mode 100644 xen/include/xen/iommu-private.h
diff --git a/xen/drivers/passthrough/device_tree.c
b/xen/drivers/passthrough/device_tree.c
index 1c32d7b50c..5796ee1f93 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -18,6 +18,7 @@
#include <xen/device_tree.h>
#include <xen/guest_access.h>
#include <xen/iommu.h>
+#include <xen/iommu-private.h>
#include <xen/lib.h>
#include <xen/sched.h>
#include <xsm/xsm.h>
@@ -83,16 +84,16 @@ fail:
return rc;
}
-static bool_t iommu_dt_device_is_assigned(const struct dt_device_node *dev)
+bool_t iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev)
{
bool_t assigned = 0;
+ ASSERT(spin_is_locked(&dtdevs_lock));
+
if ( !dt_device_is_protected(dev) )
return 0;
- spin_lock(&dtdevs_lock);
assigned = !list_empty(&dev->domain_list);
- spin_unlock(&dtdevs_lock);
return assigned;
}
@@ -213,27 +214,44 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct
domain *d,
if ( (d && d->is_dying) || domctl->u.assign_device.flags )
break;
+ /*
+ * To ensure that the dev doesn't disappear between the time we look it
+ * up with dt_find_node_by_gpath() and we check the assignment later.
+ */
+ spin_lock(&dtdevs_lock);
This change doesn't look to be explained in the commit message. But
looking at the code after this series is applied, you justified the
addition of read_lock(&dt_host_lock) to protect access to the
device-tree. This will be held longer than dtdevs_lock. So is it
actually necessary to move the locking earlier?
+
ret = dt_find_node_by_gpath(domctl->u.assign_device.u.dt.path,
domctl->u.assign_device.u.dt.size,
&dev);
if ( ret )
+ {
+ spin_unlock(&dtdevs_lock);
break;
+ }
ret = xsm_assign_dtdevice(XSM_HOOK, d, dt_node_full_name(dev));
if ( ret )
+ {
+ spin_unlock(&dtdevs_lock);
break;
+ }
if ( domctl->cmd == XEN_DOMCTL_test_assign_device )
{
- if ( iommu_dt_device_is_assigned(dev) )
+
+ if ( iommu_dt_device_is_assigned_locked(dev) )
{
printk(XENLOG_G_ERR "%s already assigned.\n",
dt_node_full_name(dev));
ret = -EINVAL;
}
+
+ spin_unlock(&dtdevs_lock);
break;
}
+ spin_unlock(&dtdevs_lock);
+
if ( d == dom_io )
return -EINVAL;
diff --git a/xen/include/xen/iommu-private.h b/xen/include/xen/iommu-private.h
new file mode 100644
index 0000000000..bb5c94e7a6
--- /dev/null
+++ b/xen/include/xen/iommu-private.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * xen/iommu-private.h
+ */
+#ifndef __XEN_IOMMU_PRIVATE_H__
+#define __XEN_IOMMU_PRIVATE_H__
+
+#ifdef CONFIG_HAS_DEVICE_TREE
+#include <xen/device_tree.h>
+
+/*
+ * Checks if dt_device_node is assigned to a domain or not. This function
+ * expects to be called with dtdevs_lock acquired by caller.
+ */
+bool_t iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev);
+#endif
+
+#endif /* __XEN_IOMMU_PRIVATE_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
Cheers,
--
Julien Grall
