[PATCH v2 2/2] PCI: Don't treat ~0 as ready in pci_dev_wait() with RRS SV

[Alexander Gruhlke]

With RRS Software Visibility, pci_dev_wait() considers a device ready as
soon as reading the Vendor ID doesn't return the RRS value.  Devices
aren't required to respond with RRS while they aren't ready, so the read
may return ~0 and pci_dev_wait() stops waiting too early.  This was seen
with Intel [8086:0a54] and Samsung [144d:a80c] NVMe SSDs.

Also wait for a Vendor ID other than ~0, except on VFs, whose Vendor ID
normally reads ~0.

Fixes: d591f6804e7e ("PCI: Wait for device readiness with Configuration RRS")
Link: https://lore.kernel.org/r/20250611101442.387378-1-hui.wang@xxxxxxxxxxxxx
Suggested-by: Lukas Wunner <lukas@xxxxxxxxx>
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Alexander Gruhlke <gruhlke@xxxxxxxxxxx>
---
 drivers/pci/pci.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 350bae907e..fef8a799c1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1213,9 +1213,10 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
 	 * initialize.
 	 *
 	 * If the device is below a Root Port with Configuration RRS
-	 * Software Visibility enabled, reading the Vendor ID returns a
+	 * Software Visibility enabled, reading the Vendor ID may return a
 	 * special data value if the device responded with RRS.  Read the
-	 * Vendor ID until we get non-RRS status.
+	 * Vendor ID until we get non-RRS status and, unless it's a VF,
+	 * something other than ~0.
 	 *
 	 * If there's no Root Port or Configuration RRS Software Visibility
 	 * is not enabled, the device may still respond with RRS, but
@@ -1235,7 +1236,8 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
 
 		if (root && root->config_rrs_sv) {
 			pci_read_config_dword(dev, PCI_VENDOR_ID, &id);
-			if (!pci_bus_rrs_vendor_id(id))
+			if (!pci_bus_rrs_vendor_id(id) &&
+			    (!PCI_POSSIBLE_ERROR(id) || dev->is_virtfn))
 				break;
 		} else {
 			pci_read_config_dword(dev, PCI_COMMAND, &id);
-- 
2.56.0