PCI/P2PDMA: Allow P2PDMA on AMD Zen and newer CPUs

Allow P2PDMA if the CPU vendor is AMD and family is 0x17 (Zen) or greater.

[bhelgaas: commit log, simplify #if/#else/#endif]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Logan Gunthorpe <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Cc: Christian König <[email protected]>
Cc: Huang Rui <[email protected]>

Author: lsgunth

drivers/pci/p2pdma.c

@@ -273,18 +273,26 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
 	seq_buf_printf(buf, "%s;", pci_name(pdev));
 }
 
+static bool cpu_supports_p2pdma(void)
+{
+#ifdef CONFIG_X86
+	struct cpuinfo_x86 *c = &cpu_data(0);
+
+	/* Any AMD CPU whose family ID is Zen or newer supports p2pdma */
+	if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17)
+		return true;
+#endif
+
+	return false;
+}
+
 static const struct pci_p2pdma_whitelist_entry {
 	unsigned short vendor;
 	unsigned short device;
 	enum {
 		REQ_SAME_HOST_BRIDGE	= 1 << 0,
 	} flags;
 } pci_p2pdma_whitelist[] = {
-	/* AMD ZEN */
-	{PCI_VENDOR_ID_AMD,	0x1450,	0},
-	{PCI_VENDOR_ID_AMD,	0x15d0,	0},
-	{PCI_VENDOR_ID_AMD,	0x1630,	0},
-
 	/* Intel Xeon E5/Core i7 */
 	{PCI_VENDOR_ID_INTEL,	0x3c00, REQ_SAME_HOST_BRIDGE},
 	{PCI_VENDOR_ID_INTEL,	0x3c01, REQ_SAME_HOST_BRIDGE},
@@ -473,7 +481,8 @@ upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
 					      acs_redirects, acs_list);
 
 	if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) {
-		if (!host_bridge_whitelist(provider, client))
+		if (!cpu_supports_p2pdma() &&
+		    !host_bridge_whitelist(provider, client))
 			map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
 	}