git: 68cbe189fdd3 - main - pci: Don't try to read cfg registers of non-existing devices

The branch main has been updated by wma:

URL: https://cgit.FreeBSD.org/src/commit/?id=68cbe189fdd3c572476f8af9219a5d335f05b51a

commit 68cbe189fdd3c572476f8af9219a5d335f05b51a
Author:     Kornel Duleba <mindal@semihalf.com>
AuthorDate: 2021-11-23 08:13:56 +0000
Commit:     Wojciech Macek <wma@FreeBSD.org>
CommitDate: 2021-11-25 08:53:40 +0000

    pci: Don't try to read cfg registers of non-existing devices
    
    Instead of returning 0xffs some controllers, such as Layerscape generate
    an external exception when someone attempts to read any register
    of config space of a non-existing device other than PCIR_VENDOR.
    This causes a kernel panic.
    Fix it by bailing during device enumeration if a device vendor register
    returns invalid value. (0xffff)
    Use this opportunity to replace some hardcoded values with a macro.
    
    I believe that this change won't have any unintended side-effects since
    it is safe to assume that vendor == 0xffff -> hdr_type == 0xffff.
    
    Sponsored by:           Alstom
    Obtained from:          Semihalf
    Reviewed by:            jhb
    MFC after:              2 weeks
    Differential revision:  https://reviews.freebsd.org/D33059
---
 sys/dev/pci/pci.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 7493ae1727fb..ecef65477137 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -683,11 +683,12 @@ pci_read_device(device_t pcib, device_t bus, int d, int b, int s, int f)
 	uint16_t vid, did;
 
 	vid = REG(PCIR_VENDOR, 2);
+	if (vid == PCIV_INVALID)
+		return (NULL);
+
 	did = REG(PCIR_DEVICE, 2);
-	if (vid != 0xffff)
-		return (pci_fill_devinfo(pcib, bus, d, b, s, f, vid, did));
 
-	return (NULL);
+	return (pci_fill_devinfo(pcib, bus, d, b, s, f, vid, did));
 }
 
 struct pci_devinfo *
@@ -4141,6 +4142,10 @@ pci_add_children(device_t dev, int domain, int busno)
 		pcifunchigh = 0;
 		f = 0;
 		DELAY(1);
+
+		/* If function 0 is not present, skip to the next slot. */
+		if (REG(PCIR_VENDOR, 2) == PCIV_INVALID)
+			continue;
 		hdrtype = REG(PCIR_HDRTYPE, 1);
 		if ((hdrtype & PCIM_HDRTYPE) > PCI_MAXHDRTYPE)
 			continue;
@@ -4182,7 +4187,7 @@ pci_rescan_method(device_t dev)
 	for (s = 0; s <= maxslots; s++) {
 		/* If function 0 is not present, skip to the next slot. */
 		f = 0;
-		if (REG(PCIR_VENDOR, 2) == 0xffff)
+		if (REG(PCIR_VENDOR, 2) == PCIV_INVALID)
 			continue;
 		pcifunchigh = 0;
 		hdrtype = REG(PCIR_HDRTYPE, 1);
@@ -4191,7 +4196,7 @@ pci_rescan_method(device_t dev)
 		if (hdrtype & PCIM_MFDEV)
 			pcifunchigh = PCIB_MAXFUNCS(pcib);
 		for (f = 0; f <= pcifunchigh; f++) {
-			if (REG(PCIR_VENDOR, 2) == 0xffff)
+			if (REG(PCIR_VENDOR, 2) == PCIV_INVALID)
 				continue;
 
 			/*