[PATCH v4 14/22] iommu/vt-d: Add custom allocator for IOASID

[Jacob Pan]

When VT-d driver runs in the guest, PASID allocation must be
performed via virtual command interface. This patch registers a
custom IOASID allocator which takes precedence over the default
XArray based allocator. The resulting IOASID allocation will always
come from the host. This ensures that PASID namespace is system-
wide.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 drivers/iommu/Kconfig       |  1 +
 drivers/iommu/intel-iommu.c | 60 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/intel-iommu.h |  2 ++
 3 files changed, 63 insertions(+)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index c40c4b5..5d1bc2a 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -213,6 +213,7 @@ config INTEL_IOMMU_SVM
 	bool "Support for Shared Virtual Memory with Intel IOMMU"
 	depends on INTEL_IOMMU && X86
 	select PCI_PASID
+	select IOASID
 	select MMU_NOTIFIER
 	select IOASID
 	help
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 09b8ff0..5b84994 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1711,6 +1711,8 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
 		if (ecap_prs(iommu->ecap))
 			intel_svm_finish_prq(iommu);
 	}
+	ioasid_unregister_allocator(&iommu->pasid_allocator);
+
 #endif
 }
 
@@ -4820,6 +4822,46 @@ static int __init platform_optin_force_iommu(void)
 	return 1;
 }
 
+#ifdef CONFIG_INTEL_IOMMU_SVM
+static ioasid_t intel_ioasid_alloc(ioasid_t min, ioasid_t max, void *data)
+{
+	struct intel_iommu *iommu = data;
+	ioasid_t ioasid;
+
+	/*
+	 * VT-d virtual command interface always uses the full 20 bit
+	 * PASID range. Host can partition guest PASID range based on
+	 * policies but it is out of guest's control.
+	 */
+	if (min < PASID_MIN || max > PASID_MAX)
+		return -EINVAL;
+
+	if (vcmd_alloc_pasid(iommu, &ioasid))
+		return INVALID_IOASID;
+
+	return ioasid;
+}
+
+static void intel_ioasid_free(ioasid_t ioasid, void *data)
+{
+	struct iommu_pasid_alloc_info *svm;
+	struct intel_iommu *iommu = data;
+
+	if (!iommu)
+		return;
+	/*
+	 * Sanity check the ioasid owner is done at upper layer, e.g. VFIO
+	 * We can only free the PASID when all the devices are unbond.
+	 */
+	svm = ioasid_find(NULL, ioasid, NULL);
+	if (!svm) {
+		pr_warn("Freeing unbond IOASID %d\n", ioasid);
+		return;
+	}
+	vcmd_free_pasid(iommu, ioasid);
+}
+#endif
+
 int __init intel_iommu_init(void)
 {
 	int ret = -ENODEV;
@@ -4924,6 +4966,24 @@ int __init intel_iommu_init(void)
 				       "%s", iommu->name);
 		iommu_device_set_ops(&iommu->iommu, &intel_iommu_ops);
 		iommu_device_register(&iommu->iommu);
+#ifdef CONFIG_INTEL_IOMMU_SVM
+		if (cap_caching_mode(iommu->cap) && sm_supported(iommu)) {
+			/*
+			 * Register a custom ASID allocator if we are running
+			 * in a guest, the purpose is to have a system wide PASID
+			 * namespace among all PASID users.
+			 * There can be multiple vIOMMUs in each guest but only
+			 * one allocator is active. All vIOMMU allocators will
+			 * eventually be calling the same host allocator.
+			 */
+			iommu->pasid_allocator.alloc = intel_ioasid_alloc;
+			iommu->pasid_allocator.free = intel_ioasid_free;
+			iommu->pasid_allocator.pdata = (void *)iommu;
+			ret = ioasid_register_allocator(&iommu->pasid_allocator);
+			if (ret)
+				pr_warn("Custom PASID allocator registeration failed\n");
+		}
+#endif
 	}
 
 	bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index bff907b..8605c74 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -31,6 +31,7 @@
 #include <linux/iommu.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/dmar.h>
+#include <linux/ioasid.h>
 
 #include <asm/cacheflush.h>
 #include <asm/iommu.h>
@@ -549,6 +550,7 @@ struct intel_iommu {
 #ifdef CONFIG_INTEL_IOMMU_SVM
 	struct page_req_dsc *prq;
 	unsigned char prq_name[16];    /* Name for PRQ interrupt */
+	struct ioasid_allocator_ops pasid_allocator; /* Custom allocator for PASIDs */
 #endif
 	struct q_inval  *qi;            /* Queued invalidation info */
 	u32 *iommu_state; /* Store iommu states between suspend and resume.*/
-- 
2.7.4