dmaengine: idxd: fix setting up priv mode for dwq

DSA spec says WQ priv bit is 0 if the Privileged Mode Enable field of the
PCI Express PASID capability is 0 and pasid is enabled. Make sure that the
WQCFG priv field is set correctly according to usage type. Reject config if
setting up kernel WQ type and no support. Also add the correct priv setup
for a descriptor.

Fixes: 484f910e93b4 ("dmaengine: idxd: fix wq config registers offset programming")
Cc: Ramesh Thomas <[e-mail]>
Signed-off-by: Dave Jiang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/Kconfig

···
 	tristate "Intel Data Accelerators support"
 	depends on PCI && X86_64 && !UML
 	depends on PCI_MSI
+	depends on PCI_PASID
 	depends on SBITMAP
 	select DMA_ENGINE
 	help

drivers/dma/idxd/device.c

···
 	return 0;
 }
 
+static bool idxd_device_pasid_priv_enabled(struct idxd_device *idxd)
+{
+	struct pci_dev *pdev = idxd->pdev;
+
+	if (pdev->pasid_enabled && (pdev->pasid_features & PCI_PASID_CAP_PRIV))
+		return true;
+	return false;
+}
+
 static int idxd_wq_config_write(struct idxd_wq *wq)
 {
 	struct idxd_device *idxd = wq->idxd;
···
 	wq->wqcfg->wq_thresh = wq->threshold;
 
 	/* byte 8-11 */
-	wq->wqcfg->priv = !!(wq->type == IDXD_WQT_KERNEL);
 	if (wq_dedicated(wq))
 		wq->wqcfg->mode = 1;
 
···
 		wq->wqcfg->pasid_en = 1;
 		if (wq->type == IDXD_WQT_KERNEL && wq_dedicated(wq))
 			wq->wqcfg->pasid = idxd->pasid;
+	}
+
+	/*
+	 * Here the priv bit is set depending on the WQ type. priv = 1 if the
+	 * WQ type is kernel to indicate privileged access. This setting only
+	 * matters for dedicated WQ. According to the DSA spec:
+	 * If the WQ is in dedicated mode, WQ PASID Enable is 1, and the
+	 * Privileged Mode Enable field of the PCI Express PASID capability
+	 * is 0, this field must be 0.
+	 *
+	 * In the case of a dedicated kernel WQ that is not able to support
+	 * the PASID cap, then the configuration will be rejected.
+	 */
+	wq->wqcfg->priv = !!(wq->type == IDXD_WQT_KERNEL);
+	if (wq_dedicated(wq) && wq->wqcfg->pasid_en &&
+	    !idxd_device_pasid_priv_enabled(idxd) &&
+	    wq->type == IDXD_WQT_KERNEL) {
+		idxd->cmd_status = IDXD_SCMD_WQ_NO_PRIV;
+		return -EOPNOTSUPP;
 	}
 
 	wq->wqcfg->priority = wq->priority;

drivers/dma/idxd/dma.c

···
 	hw->src_addr = addr_f1;
 	hw->dst_addr = addr_f2;
 	hw->xfer_size = len;
-	hw->priv = !!(wq->type == IDXD_WQT_KERNEL);
+	/*
+	 * For dedicated WQ, this field is ignored and HW will use the WQCFG.priv
+	 * field instead. This field should be set to 1 for kernel descriptors.
+	 */
+	hw->priv = 1;
 	hw->completion_addr = compl;
 }
 

include/uapi/linux/idxd.h

···
 	IDXD_SCMD_WQ_NO_SWQ_SUPPORT = 0x800c0000,
 	IDXD_SCMD_WQ_NONE_CONFIGURED = 0x800d0000,
 	IDXD_SCMD_WQ_NO_SIZE = 0x800e0000,
+	IDXD_SCMD_WQ_NO_PRIV = 0x800f0000,
 };
 
 #define IDXD_SCMD_SOFTERR_MASK	0x80000000