Re: [PATCH 4/4] dmaengine/idxd: Re-enable kernel workqueue under DMA API

Dave Jiang <dave.jiang@xxxxxxxxx> · Wed, 1 Mar 2023 18:03:17 -0700

On 3/1/23 5:59 PM, Jacob Pan wrote:
Kernel workqueues were disabled due to flawed use of kernel VA and SVA
API. Now That we have the support for attaching PASID to the device's
default domain and the ability to reserve global PASIDs from SVA APIs,
we can re-enable the kernel work queues and use them under DMA API.

We also use non-privileged access for in-kernel DMA to be consistent
with the IOMMU settings. Consequently, interrupt for user privilege is
enabled for work completion IRQs.

Link:https://lore.kernel.org/linux-iommu/20210511194726.GP1002214@xxxxxxxxxx/
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>

---
  drivers/dma/idxd/device.c | 30 +++++--------------------
  drivers/dma/idxd/init.c   | 47 +++++++++++++++++++++++++++++++++++----
  drivers/dma/idxd/sysfs.c  |  7 ------
  3 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 125652a8bb29..96faf4d3445e 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -299,21 +299,6 @@ void idxd_wqs_unmap_portal(struct idxd_device *idxd)
  	}
  }
  
-static void __idxd_wq_set_priv_locked(struct idxd_wq *wq, int priv)
-{
-	struct idxd_device *idxd = wq->idxd;
-	union wqcfg wqcfg;
-	unsigned int offset;
-
-	offset = WQCFG_OFFSET(idxd, wq->id, WQCFG_PRIVL_IDX);
-	spin_lock(&idxd->dev_lock);
-	wqcfg.bits[WQCFG_PRIVL_IDX] = ioread32(idxd->reg_base + offset);
-	wqcfg.priv = priv;
-	wq->wqcfg->bits[WQCFG_PRIVL_IDX] = wqcfg.bits[WQCFG_PRIVL_IDX];
-	iowrite32(wqcfg.bits[WQCFG_PRIVL_IDX], idxd->reg_base + offset);
-	spin_unlock(&idxd->dev_lock);
-}
-
  static void __idxd_wq_set_pasid_locked(struct idxd_wq *wq, int pasid)
  {
  	struct idxd_device *idxd = wq->idxd;
@@ -1324,15 +1309,14 @@ int drv_enable_wq(struct idxd_wq *wq)
  	}
  
  	/*
-	 * In the event that the WQ is configurable for pasid and priv bits.
-	 * For kernel wq, the driver should setup the pasid, pasid_en, and priv bit.
-	 * However, for non-kernel wq, the driver should only set the pasid_en bit for
-	 * shared wq. A dedicated wq that is not 'kernel' type will configure pasid and
+	 * In the event that the WQ is configurable for pasid, the driver
+	 * should setup the pasid, pasid_en bit. This is true for both kernel
+	 * and user shared workqueues. There is no need to setup priv bit in
+	 * that in-kernel DMA will also do user privileged requests.
+	 * A dedicated wq that is not 'kernel' type will configure pasid and
  	 * pasid_en later on so there is no need to setup.
  	 */
  	if (test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags)) {
-		int priv = 0;
-
  		if (wq_pasid_enabled(wq)) {
  			if (is_idxd_wq_kernel(wq) || wq_shared(wq)) {
  				u32 pasid = wq_dedicated(wq) ? idxd->pasid : 0;
@@ -1340,10 +1324,6 @@ int drv_enable_wq(struct idxd_wq *wq)
  				__idxd_wq_set_pasid_locked(wq, pasid);
  			}
  		}
-
-		if (is_idxd_wq_kernel(wq))
-			priv = 1;
-		__idxd_wq_set_priv_locked(wq, priv);
  	}
  
  	rc = 0;
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index f30eef701970..dadc908318aa 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -501,14 +501,52 @@ static struct idxd_device *idxd_alloc(struct pci_dev *pdev, struct idxd_driver_d
  
  static int idxd_enable_system_pasid(struct idxd_device *idxd)
  {
-	return -EOPNOTSUPP;
+	struct pci_dev *pdev = idxd->pdev;
+	struct device *dev = &pdev->dev;
+	struct iommu_domain *domain;
+	union gencfg_reg gencfg;
+	ioasid_t pasid;
+	int ret;
+
+	domain = iommu_get_domain_for_dev(dev);
+	if (!domain || domain->type == IOMMU_DOMAIN_BLOCKED)
+		return -EPERM;
+
+	pasid = iommu_sva_reserve_pasid(1, dev->iommu->max_pasids);
+	if (pasid == IOMMU_PASID_INVALID)
+		return -ENOSPC;
+
+	ret = iommu_attach_device_pasid(domain, dev, pasid);
+	if (ret) {
+		dev_err(dev, "failed to attach device pasid %d, domain type %d",
+			pasid, domain->type);
+		iommu_sva_unreserve_pasid(pasid);
+		return ret;
+	}
+
+	/* Since we set user privilege for kernel DMA, enable completion IRQ */
+	gencfg.bits = ioread32(idxd->reg_base + IDXD_GENCFG_OFFSET);
+	gencfg.user_int_en = 1;
+	iowrite32(gencfg.bits, idxd->reg_base + IDXD_GENCFG_OFFSET);
+	idxd->pasid = pasid;
+
+	return ret;
  }
  
  static void idxd_disable_system_pasid(struct idxd_device *idxd)
  {
+	struct pci_dev *pdev = idxd->pdev;
+	struct device *dev = &pdev->dev;
+	struct iommu_domain *domain;
+
+	domain = iommu_get_domain_for_dev(dev);
+	if (!domain || domain->type == IOMMU_DOMAIN_BLOCKED)
+		return;
  
-	iommu_sva_unbind_device(idxd->sva);
+	iommu_detach_device_pasid(domain, dev, idxd->pasid);
+	iommu_sva_unreserve_pasid(idxd->pasid);
  	idxd->sva = NULL;
+	idxd->pasid = IOMMU_PASID_INVALID;
  }
  
  static int idxd_probe(struct idxd_device *idxd)
@@ -530,8 +568,9 @@ static int idxd_probe(struct idxd_device *idxd)
  		} else {
  			set_bit(IDXD_FLAG_USER_PASID_ENABLED, &idxd->flags);
  
-			if (idxd_enable_system_pasid(idxd))
-				dev_warn(dev, "No in-kernel DMA with PASID.\n");
+			rc = idxd_enable_system_pasid(idxd);
+			if (rc)
+				dev_warn(dev, "No in-kernel DMA with PASID. %d\n", rc);
  			else
  				set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags);
  		}
diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
index 3229dfc78650..09f5c3f2a992 100644
--- a/drivers/dma/idxd/sysfs.c
+++ b/drivers/dma/idxd/sysfs.c
@@ -944,13 +944,6 @@ static ssize_t wq_name_store(struct device *dev,
  	if (strlen(buf) > WQ_NAME_SIZE || strlen(buf) == 0)
  		return -EINVAL;
  
-	/*
-	 * This is temporarily placed here until we have SVM support for
-	 * dmaengine.
-	 */
-	if (wq->type == IDXD_WQT_KERNEL && device_pasid_enabled(wq->idxd))
-		return -EOPNOTSUPP;
-
  	input = kstrndup(buf, count, GFP_KERNEL);
  	if (!input)
  		return -ENOMEM;






