Emulate the Device ID and Vendor ID registers for VFs

The SR-IOV standard requires VFs to read all-ones when the VID
and DID registers are read.  The VMM (hypervisor) is required to
emulate them instead.  Make pci_read_config() do this emulation.

Change pci_user.c to use pci_read_config() to read config space
registers instead of going directly to the pcib so that the
emulated VID/DID registers work correctly on VFs.  This is
required both for pciconf and bhyve PCI passthrough.

Differential Revision:	https://reviews.freebsd.org/D77
Reviewed by:		jhb
MFC after: 		1 month
Sponsored by:		Sandvine Inc.

1 files changed, 31 insertions, 0 deletions

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 517e91e..e103f04 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -4880,6 +4880,37 @@ pci_read_config_method(device_t dev, device_t child, int reg, int width)
 	struct pci_devinfo *dinfo = device_get_ivars(child);
 	pcicfgregs *cfg = &dinfo->cfg;
 
+#ifdef PCI_IOV
+	/*
+	 * SR-IOV VFs don't implement the VID or DID registers, so we have to
+	 * emulate them here.
+	 */
+	if (cfg->flags & PCICFG_VF) {
+		if (reg == PCIR_VENDOR) {
+			switch (width) {
+			case 4:
+				return (cfg->device << 16 | cfg->vendor);
+			case 2:
+				return (cfg->vendor);
+			case 1:
+				return (cfg->vendor & 0xff);
+			default:
+				return (0xffffffff);
+			}
+		} else if (reg == PCIR_DEVICE) {
+			switch (width) {
+			/* Note that an unaligned 4-byte read is an error. */
+			case 2:
+				return (cfg->device);
+			case 1:
+				return (cfg->device & 0xff);
+			default:
+				return (0xffffffff);
+			}
+		}
+	}
+#endif
+
 	return (PCIB_READ_CONFIG(device_get_parent(dev),
 	    cfg->bus, cfg->slot, cfg->func, reg, width));
 }