[PATCH V4 04/18] iommu/ioasid: Support setting system-wide capacity

Jacob Pan
2021-02-28T06:36:53Z

IOASID is a system-wide resource that could vary on different systems.
The default capacity is 20 bits as defined in the PCI-E specifications.
This patch adds a function to allow adjusting system IOASID capacity.
For VT-d this is set during boot as part of the Intel IOMMU
initialization. APIs also added to support runtime capacity reservation,
potentially by cgroups.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
drivers/iommu/intel/iommu.c | 5 +++
drivers/iommu/ioasid.c | 70 +++++++++++++++++++++++++++++++++++++
include/linux/ioasid.h | 18 ++++++++++
3 files changed, 93 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index f665322a0991..6f42ff7d171d 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -41,6 +41,7 @@
#include <linux/dma-direct.h>
#include <linux/crash_dump.h>
#include <linux/numa.h>
+#include <linux/ioasid.h>
#include <asm/irq_remapping.h>
#include <asm/cacheflush.h>
#include <asm/iommu.h>
@@ -3298,6 +3299,10 @@ static int __init init_dmars(void)
if (ret)
goto free_iommu;

+ /* PASID is needed for scalable mode irrespective to SVM */
+ if (intel_iommu_sm)
+ ioasid_install_capacity(intel_pasid_max_id);
+
/*
* for each drhd
* enable fault log
diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index 4eb9b3dd1b85..28681b99340b 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c
@@ -10,6 +10,10 @@
#include <linux/spinlock.h>
#include <linux/xarray.h>

+/* Default to PCIe standard 20 bit PASID */
+#define PCI_PASID_MAX 0x100000
+static ioasid_t ioasid_capacity = PCI_PASID_MAX;
+static ioasid_t ioasid_capacity_avail = PCI_PASID_MAX;
struct ioasid_data {
ioasid_t id;
struct ioasid_set *set;
@@ -258,6 +262,72 @@ void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops)
}
EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);

+void ioasid_install_capacity(ioasid_t total)
+{
+ spin_lock(&ioasid_allocator_lock);
+ if (ioasid_capacity && ioasid_capacity != PCI_PASID_MAX) {
+ pr_warn("IOASID capacity is already set.\n");
+ goto done_unlock;
+ }
+ ioasid_capacity = ioasid_capacity_avail = total;
+done_unlock:
+ spin_unlock(&ioasid_allocator_lock);
+}
+EXPORT_SYMBOL_GPL(ioasid_install_capacity);
+
+/**
+ * @brief Reserve capacity from the system pool
+ *
+ * @param nr_ioasid Number of IOASIDs requested to be reserved, 0 means
+ * reserve all remaining IDs.
+ *
+ * @return the remaining capacity on success, or errno
+ */
+int ioasid_reserve_capacity(ioasid_t nr_ioasid)
+{
+ int ret = 0;
+
+ spin_lock(&ioasid_allocator_lock);
+ if (nr_ioasid > ioasid_capacity_avail) {
+ ret = -ENOSPC;
+ goto done_unlock;
+ }
+ if (!nr_ioasid)
+ nr_ioasid = ioasid_capacity_avail;
+ ioasid_capacity_avail -= nr_ioasid;
+ ret = nr_ioasid;
+done_unlock:
+ spin_unlock(&ioasid_allocator_lock);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ioasid_reserve_capacity);
+
+/**
+ * @brief Return capacity to the system pool
+ * We trust the caller not to return more than it has reserved, we could
+ * also track reservation if needed.
+ *
+ * @param nr_ioasid Number of IOASIDs requested to be returned
+ *
+ * @return the remaining capacity on success, or errno
+ */
+int ioasid_cancel_capacity(ioasid_t nr_ioasid)
+{
+ int ret = 0;
+
+ spin_lock(&ioasid_allocator_lock);
+ if (nr_ioasid + ioasid_capacity_avail > ioasid_capacity) {
+ ret = -EINVAL;
+ goto done_unlock;
+ }
+ ioasid_capacity_avail += nr_ioasid;
+ ret = ioasid_capacity_avail;
+done_unlock:
+ spin_unlock(&ioasid_allocator_lock);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ioasid_cancel_capacity);
+
/**
* ioasid_attach_data - Set private data for an allocated ioasid
* @ioasid: the ID to set data
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index f6e705f832f0..2780bdc84b94 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h
@@ -32,6 +32,10 @@ struct ioasid_allocator_ops {
#define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 }

#if IS_ENABLED(CONFIG_IOASID)
+void ioasid_install_capacity(ioasid_t total);
+int ioasid_reserve_capacity(ioasid_t nr_ioasid);
+int ioasid_cancel_capacity(ioasid_t nr_ioasid);
+
ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
void *private);
void ioasid_get(ioasid_t ioasid);
@@ -43,6 +47,20 @@ void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator);
int ioasid_attach_data(ioasid_t ioasid, void *data);
void ioasid_detach_data(ioasid_t ioasid);
#else /* !CONFIG_IOASID */
+static inline void ioasid_install_capacity(ioasid_t total)
+{
+}
+
+static inline int ioasid_reserve_capacity(ioasid_t nr_ioasid)
+{
+ return -ENOSPC;
+}
+
+static inline int ioasid_cancel_capacity(ioasid_t nr_ioasid)
+{
+ return -EINVAL;
+}
+
static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
ioasid_t max, void *private)
{
--
2.25.1