iommu/vt-d: Introduce a rwsem to protect global data structures
Introduce a global rwsem dmar_global_lock, which will be used to
protect DMAR related global data structures from DMAR/PCI/memory
device hotplug operations in process context.
DMA and interrupt remapping related data structures are read most,
and only change when memory/PCI/DMAR hotplug event happens.
So a global rwsem solution is adopted for balance between simplicity
and performance.
For interrupt remapping driver, function intel_irq_remapping_supported(),
dmar_table_init(), intel_enable_irq_remapping(), disable_irq_remapping(),
reenable_irq_remapping() and enable_drhd_fault_handling() etc
are called during booting, suspending and resuming with interrupt
disabled, so no need to take the global lock.
For interrupt remapping entry allocation, the locking model is:
down_read(&dmar_global_lock);
/* Find corresponding iommu */
iommu = map_hpet_to_ir(id);
if (iommu)
/*
* Allocate remapping entry and mark entry busy,
* the IOMMU won't be hot-removed until the
* allocated entry has been released.
*/
index = alloc_irte(iommu, irq, 1);
up_read(&dmar_global_lock);
For DMA remmaping driver, we only uses the dmar_global_lock rwsem to
protect functions which are only called in process context. For any
function which may be called in interrupt context, we will use RCU
to protect them in following patches.
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index bb98e37..50d639a 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3637,11 +3637,13 @@
if (!domain)
return 0;
+ down_read(&dmar_global_lock);
domain_remove_one_dev_info(domain, pdev);
if (!(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) &&
!(domain->flags & DOMAIN_FLAG_STATIC_IDENTITY) &&
list_empty(&domain->devices))
domain_exit(domain);
+ up_read(&dmar_global_lock);
return 0;
}
@@ -3659,6 +3661,13 @@
/* VT-d is required for a TXT/tboot launch, so enforce that */
force_on = tboot_force_iommu();
+ if (iommu_init_mempool()) {
+ if (force_on)
+ panic("tboot: Failed to initialize iommu memory\n");
+ return -ENOMEM;
+ }
+
+ down_write(&dmar_global_lock);
if (dmar_table_init()) {
if (force_on)
panic("tboot: Failed to initialize DMAR table\n");
@@ -3681,12 +3690,6 @@
if (no_iommu || dmar_disabled)
goto out_free_dmar;
- if (iommu_init_mempool()) {
- if (force_on)
- panic("tboot: Failed to initialize iommu memory\n");
- goto out_free_dmar;
- }
-
if (list_empty(&dmar_rmrr_units))
printk(KERN_INFO "DMAR: No RMRR found\n");
@@ -3696,7 +3699,7 @@
if (dmar_init_reserved_ranges()) {
if (force_on)
panic("tboot: Failed to reserve iommu ranges\n");
- goto out_free_mempool;
+ goto out_free_reserved_range;
}
init_no_remapping_devices();
@@ -3708,6 +3711,7 @@
printk(KERN_ERR "IOMMU: dmar init failed\n");
goto out_free_reserved_range;
}
+ up_write(&dmar_global_lock);
printk(KERN_INFO
"PCI-DMA: Intel(R) Virtualization Technology for Directed I/O\n");
@@ -3729,10 +3733,10 @@
out_free_reserved_range:
put_iova_domain(&reserved_iova_list);
-out_free_mempool:
- iommu_exit_mempool();
out_free_dmar:
intel_iommu_free_dmars();
+ up_write(&dmar_global_lock);
+ iommu_exit_mempool();
return ret;
}