linux-kernel - [PATCH v2] PCI: Add DMA alias quirk for PLX PEX NTB

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Message-Id: <6A902F0D-FE98-4760-ADBB-4D5987D866BE@arista.com>
Date:   Tue, 26 Nov 2019 17:03:23 +0000
From:   James Sewart <jamessewart@...sta.com>
To:     linux-pci@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: [PATCH v2] PCI: Add DMA alias quirk for PLX PEX NTB

The PLX PEX NTB forwards DMA transactions using Requester ID's that
don't exist as PCI devices. The devfn for a transaction is used as an
index into a lookup table storing the origin of a transaction on the
other side of the bridge.

Add helper pci_add_dma_alias_range that can alias a range of devfns in 
dma_alias_mask.

This patch aliases all possible devfn's to the NTB device so that any
transaction coming in is governed by the mappings for the NTB.

Signed-off-by: James Sewart <jamessewart@...sta.com>
---
 drivers/pci/pci.c    | 29 ++++++++++++++++++++++-------
 drivers/pci/quirks.c | 15 +++++++++++++++
 include/linux/pci.h  |  1 +
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a97e2571a527..f502af1b5d10 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5854,6 +5854,18 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
 	return 0;
 }
 
+int _pci_add_dma_alias_range(struct pci_dev *dev, u8 devfn_from, int len)
+{
+	if (!dev->dma_alias_mask)
+		dev->dma_alias_mask = bitmap_zalloc(U8_MAX, GFP_KERNEL);
+	if (!dev->dma_alias_mask) {
+		pci_warn(dev, "Unable to allocate DMA alias mask\n");
+		return -ENOMEM;
+	}
+	bitmap_set(dev->dma_alias_mask, devfn_from, len);
+	return 0;
+}
+
 /**
  * pci_add_dma_alias - Add a DMA devfn alias for a device
  * @dev: the PCI device for which alias is added
@@ -5875,18 +5887,21 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
  */
 void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
 {
-	if (!dev->dma_alias_mask)
-		dev->dma_alias_mask = bitmap_zalloc(U8_MAX, GFP_KERNEL);
-	if (!dev->dma_alias_mask) {
-		pci_warn(dev, "Unable to allocate DMA alias mask\n");
+	if (_pci_add_dma_alias_range(dev, devfn, 1) != 0)
 		return;
-	}
-
-	set_bit(devfn, dev->dma_alias_mask);
 	pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
 		 PCI_SLOT(devfn), PCI_FUNC(devfn));
 }
 
+void pci_add_dma_alias_range(struct pci_dev *dev, u8 devfn_from, int len)
+{
+	int devfn_to = devfn_from + len - 1;
+	if (_pci_add_dma_alias_range(dev, devfn_from, len) != 0)
+		return;
+	pci_info(dev, "Enabling fixed DMA alias for devfn range from %02x.%d to %02x.%d\n",
+		 PCI_SLOT(devfn_from), PCI_FUNC(devfn_from), PCI_SLOT(devfn_to), PCI_FUNC(devfn_to));
+}
+
 bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2)
 {
 	return (dev1->dma_alias_mask &&
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 320255e5e8f8..1ed230f739a4 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5315,6 +5315,21 @@ SWITCHTEC_QUIRK(0x8574);  /* PFXI 64XG3 */
 SWITCHTEC_QUIRK(0x8575);  /* PFXI 80XG3 */
 SWITCHTEC_QUIRK(0x8576);  /* PFXI 96XG3 */
 
+/*
+ * PLX NTB uses devfn proxy IDs to move TLPs between NT endpoints. These IDs
+ * are used to forward responses to the originator on the other side of the
+ * NTB. Alias all possible IDs to the NTB to permit access when the IOMMU is
+ * turned on.
+ */
+static void quirk_plx_ntb_dma_alias(struct pci_dev *pdev)
+{
+	pci_info(pdev, "Setting PLX NTB proxy ID aliases\n");
+	/* PLX NTB may use all 256 devfns */
+	pci_add_dma_alias_range(pdev, 0, 256);
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_PLX, 0x87b0, quirk_plx_ntb_dma_alias);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_PLX, 0x87b1, quirk_plx_ntb_dma_alias);
+
 /*
  * On Lenovo Thinkpad P50 SKUs with a Nvidia Quadro M1000M, the BIOS does
  * not always reset the secondary Nvidia GPU between reboots if the system
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 1a6cf19eac2d..6765f3d0102b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2324,6 +2324,7 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
 #endif
 
 void pci_add_dma_alias(struct pci_dev *dev, u8 devfn);
+void pci_add_dma_alias_range(struct pci_dev *dev, u8 devfn_from, int len);
 bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2);
 int pci_for_each_dma_alias(struct pci_dev *pdev,
 			   int (*fn)(struct pci_dev *pdev,
-- 
2.24.0