[PULL,02/48] pci: ensure valid link status bits for downstream ports

Commit Message

Michael S. Tsirkin Jan. 15, 2025, 6:08 p.m. UTC

From: Sebastian Ott <[e-mail]>

PCI hotplug for downstream endpoints on arm fails because Linux'
PCIe hotplug driver doesn't like the QEMU provided LNKSTA:

  pcieport 0000:08:01.0: pciehp: Slot(2): Card present
  pcieport 0000:08:01.0: pciehp: Slot(2): Link Up
  pcieport 0000:08:01.0: pciehp: Slot(2): Cannot train link: status 0x2000

There's 2 cases where LNKSTA isn't setup properly:
* the downstream device has no express capability
* max link width of the bridge is 0

Move the sanity checks added via 88c869198aa63
("pci: Sanity test minimum downstream LNKSTA") outside of the
branch to make sure downstream ports always have a valid LNKSTA.

Signed-off-by: Sebastian Ott <[e-mail]>
Tested-by: Zhenyu Zhang <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Alex Williamson <[e-mail]>
Reviewed-by: Michael S. Tsirkin <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
---
 hw/pci/pcie.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

Patch

diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index 0b455c8654..1b12db6fa2 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -1113,18 +1113,22 @@  void pcie_sync_bridge_lnk(PCIDevice *bridge_dev)
         if ((lnksta & PCI_EXP_LNKSTA_NLW) > (lnkcap & PCI_EXP_LNKCAP_MLW)) {
             lnksta &= ~PCI_EXP_LNKSTA_NLW;
             lnksta |= lnkcap & PCI_EXP_LNKCAP_MLW;
-        } else if (!(lnksta & PCI_EXP_LNKSTA_NLW)) {
-            lnksta |= QEMU_PCI_EXP_LNKSTA_NLW(QEMU_PCI_EXP_LNK_X1);
         }
 
         if ((lnksta & PCI_EXP_LNKSTA_CLS) > (lnkcap & PCI_EXP_LNKCAP_SLS)) {
             lnksta &= ~PCI_EXP_LNKSTA_CLS;
             lnksta |= lnkcap & PCI_EXP_LNKCAP_SLS;
-        } else if (!(lnksta & PCI_EXP_LNKSTA_CLS)) {
-            lnksta |= QEMU_PCI_EXP_LNKSTA_CLS(QEMU_PCI_EXP_LNK_2_5GT);
         }
     }
 
+    if (!(lnksta & PCI_EXP_LNKSTA_NLW)) {
+        lnksta |= QEMU_PCI_EXP_LNKSTA_NLW(QEMU_PCI_EXP_LNK_X1);
+    }
+
+    if (!(lnksta & PCI_EXP_LNKSTA_CLS)) {
+        lnksta |= QEMU_PCI_EXP_LNKSTA_CLS(QEMU_PCI_EXP_LNK_2_5GT);
+    }
+
     pci_word_test_and_clear_mask(exp_cap + PCI_EXP_LNKSTA,
                                  PCI_EXP_LNKSTA_CLS | PCI_EXP_LNKSTA_NLW);
     pci_word_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA, lnksta &