linux-kernel - [PATCH v1] Intel Sky Lake-E host root ports check.

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Message-Id: <20220321143120.12191-1-shlomop@pliops.com>
Date:   Mon, 21 Mar 2022 16:31:20 +0200
From:   Shlomo Pongratz <shlomopongratz@...il.com>
To:     linux-pci@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, andrew.maier@...eticom.com,
        logang@...tatee.com, bhelgaas@...gle.com,
        Shlomo Pongratz <shlomop@...ops.com>
Subject: [PATCH v1] Intel Sky Lake-E host root ports check.

On commit 7b94b53db34f ("PCI/P2PDMA: Add Intel Sky Lake-E Root Ports B, C, D to the whitelist")
Andrew Maier added the Sky Lake-E additional devices
2031, 2032 and 2033 root ports to the already existing 2030 device.
Note that the Intel devices 2030, 2031, 2032 and 2033 are ports A, B, C and D.
Consider on a bus X only port C is connected downstream so in the PCI scan only
device 8086:2032 on 0000:X:02.0 will be found as bridges that have no children are ignored.
As a result the routine pci_host_bridge_dev will return NULL for devices under slot C.
In the proposed patch port field is added to the whitelist which is 0 for 2030, 1 for 2031,
2 for 2032 3 for 2033 and 0 for all other devices.

Signed-off-by: Shlomo Pongratz <shlomop@...ops.com>
---
 drivers/pci/p2pdma.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 1015274bd2fe..86f6594a0b8a 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -305,22 +305,23 @@ static bool cpu_supports_p2pdma(void)
 static const struct pci_p2pdma_whitelist_entry {
 	unsigned short vendor;
 	unsigned short device;
+	unsigned short port;
 	enum {
 		REQ_SAME_HOST_BRIDGE	= 1 << 0,
 	} flags;
 } pci_p2pdma_whitelist[] = {
 	/* Intel Xeon E5/Core i7 */
-	{PCI_VENDOR_ID_INTEL,	0x3c00, REQ_SAME_HOST_BRIDGE},
-	{PCI_VENDOR_ID_INTEL,	0x3c01, REQ_SAME_HOST_BRIDGE},
+	{PCI_VENDOR_ID_INTEL,	0x3c00, 0, REQ_SAME_HOST_BRIDGE},
+	{PCI_VENDOR_ID_INTEL,	0x3c01, 0, REQ_SAME_HOST_BRIDGE},
 	/* Intel Xeon E7 v3/Xeon E5 v3/Core i7 */
-	{PCI_VENDOR_ID_INTEL,	0x2f00, REQ_SAME_HOST_BRIDGE},
-	{PCI_VENDOR_ID_INTEL,	0x2f01, REQ_SAME_HOST_BRIDGE},
+	{PCI_VENDOR_ID_INTEL,	0x2f00, 0, REQ_SAME_HOST_BRIDGE},
+	{PCI_VENDOR_ID_INTEL,	0x2f01, 0, REQ_SAME_HOST_BRIDGE},
 	/* Intel SkyLake-E */
-	{PCI_VENDOR_ID_INTEL,	0x2030, 0},
-	{PCI_VENDOR_ID_INTEL,	0x2031, 0},
-	{PCI_VENDOR_ID_INTEL,	0x2032, 0},
-	{PCI_VENDOR_ID_INTEL,	0x2033, 0},
-	{PCI_VENDOR_ID_INTEL,	0x2020, 0},
+	{PCI_VENDOR_ID_INTEL,	0x2030, 0, 0},
+	{PCI_VENDOR_ID_INTEL,	0x2031, 1, 0},
+	{PCI_VENDOR_ID_INTEL,	0x2032, 2, 0},
+	{PCI_VENDOR_ID_INTEL,	0x2033, 3, 0},
+	{PCI_VENDOR_ID_INTEL,	0x2020, 0, 0},
 	{}
 };
 
@@ -332,6 +333,11 @@ static const struct pci_p2pdma_whitelist_entry {
  * bus->devices list and that the devfn is 00.0. These assumptions should hold
  * for all the devices in the whitelist above.
  *
+ * The method above will work in most cases but not for all.
+ * Note that the Intel devices 2030, 2031, 2032 and 2033 are ports A, B, C and D.
+ * Consider on a bus X only port C is connected downstream so in the PCI scan only
+ * device 8086:2032 on 0000:X:02.0 will be found as birdges with no children are ignored
+ *
  * This function is equivalent to pci_get_slot(host->bus, 0), however it does
  * not take the pci_bus_sem lock seeing __host_bridge_whitelist() must not
  * sleep.
@@ -349,7 +355,10 @@ static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
 
 	if (!root)
 		return NULL;
-	if (root->devfn != PCI_DEVFN(0, 0))
+	/* Here just check that the function is 0
+	 * The slot number will be checked later
+	 */
+	if (PCI_FUNC(root->devfn) != 0)
 		return NULL;
 
 	return root;
@@ -371,6 +380,12 @@ static bool __host_bridge_whitelist(struct pci_host_bridge *host,
 	for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
 		if (vendor != entry->vendor || device != entry->device)
 			continue;
+		/* For Intel Sky Lake-E host root ports check the port is
+		 * Identical to the slot number.
+		 * For other devices continue to inssist on slot 0
+		 */
+		if (PCI_SLOT(root->devfn) != entry->port)
+			return false;
 		if (entry->flags & REQ_SAME_HOST_BRIDGE && !same_host_bridge)
 			return false;
 
-- 
2.17.1