[PATCH v3 3/4] iommu/vt-d: Add page request draining support

Lu Baolu
2020-04-22T08:09:35Z

When a PASID is stopped or terminated, there can be pending PRQs
(requests that haven't received responses) in remapping hardware.
This adds the interface to drain page requests and call it when a
PASID is terminated.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/iommu/intel-svm.c | 103 ++++++++++++++++++++++++++++++++++--
include/linux/intel-iommu.h | 4 ++
2 files changed, 102 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 83dc4319f661..2534641ef707 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -23,6 +23,7 @@
#include "intel-pasid.h"

static irqreturn_t prq_event_thread(int irq, void *d);
+static void intel_svm_drain_prq(struct device *dev, int pasid);

#define PRQ_ORDER 0

@@ -66,6 +67,8 @@ int intel_svm_enable_prq(struct intel_iommu *iommu)
dmar_writeq(iommu->reg + DMAR_PQT_REG, 0ULL);
dmar_writeq(iommu->reg + DMAR_PQA_REG, virt_to_phys(iommu->prq) | PRQ_ORDER);

+ init_completion(&iommu->prq_complete);
+
return 0;
}

@@ -208,6 +211,7 @@ static void intel_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
rcu_read_lock();
list_for_each_entry_rcu(sdev, &svm->devs, list) {
intel_pasid_tear_down_entry(svm->iommu, sdev->dev, svm->pasid);
+ intel_svm_drain_prq(sdev->dev, svm->pasid);
intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
}
rcu_read_unlock();
@@ -401,12 +405,8 @@ int intel_svm_unbind_gpasid(struct device *dev, int pasid)
if (!sdev->users) {
list_del_rcu(&sdev->list);
intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
+ intel_svm_drain_prq(dev, svm->pasid);
intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
- /* TODO: Drain in flight PRQ for the PASID since it
- * may get reused soon, we don't want to
- * confuse with its previous life.
- * intel_svm_drain_prq(dev, pasid);
- */
kfree_rcu(sdev, rcu);

if (list_empty(&svm->devs)) {
@@ -644,6 +644,7 @@ int intel_svm_unbind_mm(struct device *dev, int pasid)
* large and has to be physically contiguous. So it's
* hard to be as defensive as we might like. */
intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
+ intel_svm_drain_prq(dev, svm->pasid);
intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
kfree_rcu(sdev, rcu);

@@ -722,6 +723,92 @@ static bool is_canonical_address(u64 addr)
return (((saddr << shift) >> shift) == saddr);
}

+/**
+ * intel_svm_drain_prq:
+ *
+ * Drain all pending page requests and responses related to a specific
+ * pasid in both software and hardware.
+ */
+static void intel_svm_drain_prq(struct device *dev, int pasid)
+{
+ struct device_domain_info *info;
+ struct dmar_domain *domain;
+ struct intel_iommu *iommu;
+ struct qi_desc desc[3];
+ struct pci_dev *pdev;
+ int head, tail;
+ u16 sid, did;
+ int qdep;
+
+ info = get_domain_info(dev);
+ if (WARN_ON(!info || !dev_is_pci(dev)))
+ return;
+
+ if (!info->ats_enabled)
+ return;
+
+ iommu = info->iommu;
+ domain = info->domain;
+ pdev = to_pci_dev(dev);
+ sid = PCI_DEVID(info->bus, info->devfn);
+ did = domain->iommu_did[iommu->seq_id];
+ qdep = pci_ats_queue_depth(pdev);
+
+ memset(desc, 0, sizeof(desc));
+ desc[0].qw0 = QI_IWD_STATUS_DATA(QI_DONE) |
+ QI_IWD_FENCE |
+ QI_IWD_TYPE;
+ desc[1].qw0 = QI_EIOTLB_PASID(pasid) |
+ QI_EIOTLB_DID(did) |
+ QI_EIOTLB_GRAN(QI_GRAN_NONG_PASID) |
+ QI_EIOTLB_TYPE;
+ desc[2].qw0 = QI_DEV_EIOTLB_PASID(pasid) |
+ QI_DEV_EIOTLB_SID(sid) |
+ QI_DEV_EIOTLB_QDEP(qdep) |
+ QI_DEIOTLB_TYPE |
+ QI_DEV_IOTLB_PFSID(info->pfsid);
+
+ /*
+ * Submit an invalidation wait descriptor with fence and page request
+ * drain flags set to invalidation queue. This ensures that all requests
+ * submitted to the invalidation queue ahead of this wait descriptor are
+ * processed and completed, and all already issued page requests from
+ * the device are put in the page request queue.
+ */
+ qi_submit_sync(iommu, desc, 1, QI_OPT_WAIT_DRAIN);
+
+ /*
+ * Check and wait until all pending page requests in the queue are
+ * handled by the intr thread.
+ */
+prq_retry:
+ tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
+ head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+ while (head != tail) {
+ struct page_req_dsc *req;
+
+ req = &iommu->prq[head / sizeof(*req)];
+ if (!req->pasid_present || req->pasid != pasid) {
+ head = (head + sizeof(*req)) & PRQ_RING_MASK;
+ continue;
+ }
+
+ wait_for_completion_timeout(&iommu->prq_complete, HZ);
+ goto prq_retry;
+ }
+
+ /*
+ * Perform steps described in VT-d spec CH7.10 to drain page
+ * requests and responses in hardware.
+ */
+qi_retry:
+ qi_submit_sync(iommu, desc, 3, QI_OPT_WAIT_DRAIN);
+ if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) {
+ wait_for_completion_timeout(&iommu->prq_complete, HZ);
+ goto qi_retry;
+ }
+}
+
static irqreturn_t prq_event_thread(int irq, void *d)
{
struct intel_iommu *iommu = d;
@@ -856,6 +943,12 @@ static irqreturn_t prq_event_thread(int irq, void *d)
}

dmar_writeq(iommu->reg + DMAR_PQH_REG, tail);
+ /*
+ * Clear the page request overflow bit and wake up all threads that
+ * are waiting for the completion of this handling.
+ */
+ writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG);
+ complete(&iommu->prq_complete);

return IRQ_RETVAL(handled);
}
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index cca1e5f9aeaa..a0512b401a59 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -292,6 +292,8 @@

/* PRS_REG */
#define DMA_PRS_PPR ((u32)1)
+#define DMA_PRS_PRO ((u32)2)
+
#define DMA_VCS_PAS ((u64)1)

#define IOMMU_WAIT_OP(iommu, offset, op, cond, sts) \
@@ -333,6 +335,7 @@ enum {

#define QI_IWD_STATUS_DATA(d) (((u64)d) << 32)
#define QI_IWD_STATUS_WRITE (((u64)1) << 5)
+#define QI_IWD_FENCE (((u64)1) << 6)
#define QI_IWD_PRQ_DRAIN (((u64)1) << 7)

#define QI_IOTLB_DID(did) (((u64)did) << 16)
@@ -590,6 +593,7 @@ struct intel_iommu {
#ifdef CONFIG_INTEL_IOMMU_SVM
struct page_req_dsc *prq;
unsigned char prq_name[16]; /* Name for PRQ interrupt */
+ struct completion prq_complete;
struct ioasid_allocator_ops pasid_allocator; /* Custom allocator for PASIDs */
#endif
struct q_inval *qi; /* Queued invalidation info */
--
2.17.1