Re: [PATCH v6 02/10] iommu/vt-d: Add custom allocator for IOASID
From: Lu Baolu
Date: Tue Oct 22 2019 - 22:24:45 EST
Hi,
On 10/23/19 8:51 AM, Raj, Ashok wrote:
On Tue, Oct 22, 2019 at 04:53:15PM -0700, Jacob Pan wrote:
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 | 67 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/intel-iommu.h | 2 ++
3 files changed, 70 insertions(+)
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index fd50ddffffbf..961fe5795a90 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -211,6 +211,7 @@ 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
help
Shared Virtual Memory (SVM) provides a facility for devices
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 3f974919d3bd..3aff0141c522 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1706,6 +1706,8 @@ 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
}
@@ -4910,6 +4912,46 @@ static int __init probe_acpi_namespace_devices(void)
return 0;
}
+#ifdef CONFIG_INTEL_IOMMU_SVM
Maybe move them to intel-svm.c instead? that's where the bulk
of the svm support is?
I think this is a generic PASID allocator for guest IOMMU although vSVA
is currently the only consumer. Instead of making it SVM specific, I'd
like to suggest moving it to intel-pasid.c and replace the @svm
parameter with a void * one in intel_ioasid_free().
+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 INVALID_IOASID;
What are these PASID_MIN/MAX? Do you check if these are within the
limits supported by the iommu/vIOMMU as its enumerated?
Is it an invalid request when @max is greater than hardware capability?
Say, the consumer is asking for allocate a PASID within [0, 2^20], while
the PASID pool of the allocator is just, say, [4, 2^19] with others
reserved for other special usage or due to iommu capability. Instead
of returning error, why not just allocating a PASID within [2, 2^19]?
In another word, final allocation range should be Range[allocator
supported] & Range[customer specified]. Please correct me if I missed
anything.
+
+ 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;
@@ -5020,6 +5062,31 @@ 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)) {
do you need to check against cap_caching_mode() or ecap_vcmd?
+ /*
+ * 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");
+ /*
+ * Disable scalable mode on this IOMMU if there
+ * is no custom allocator. Mixing SM capable vIOMMU
+ * and non-SM vIOMMU are not supported.
+ */
+ intel_iommu_sm = 0;
+ }
+ }
+#endif
I think this should also be moved to intel-pasid.c and made it svm
independent as a generic pasid allocator for IOMMU running in a vm guest
or user level application.
Best regards,
baolu
}
bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index eea7468694a7..fb1973a761c1 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -19,6 +19,7 @@
#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>
@@ -542,6 +543,7 @@ 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