linux-kernel - [PATCH] PCI/aspm: Fix link->downstream setting

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Date:   Wed,  1 Mar 2017 00:25:40 -0800
From:   Yinghai Lu <yinghai@...nel.org>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Rajat Jain <rajatja@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH] PCI/aspm: Fix link->downstream setting

~ # echo 1 > /sys/bus/pci/devices/0000\:0b\:00.0/remove
...
 BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
 IP: pcie_config_aspm_link+0x5d/0x2b0
 Call Trace:
  pcie_aspm_exit_link_state+0x75/0x130
  pci_stop_bus_device+0xa4/0xb0
  pci_stop_and_remove_bus_device_locked+0x1a/0x30
  remove_store+0x50/0x70
  dev_attr_store+0x18/0x30
  sysfs_kf_write+0x44/0x60
  kernfs_fop_write+0x10e/0x190
  __vfs_write+0x28/0x110
  ? rcu_read_lock_sched_held+0x5d/0x80
  ? rcu_sync_lockdep_assert+0x2c/0x60
  ? __sb_start_write+0x173/0x1a0
  ? vfs_write+0xb3/0x180
  vfs_write+0xc4/0x180
  SyS_write+0x49/0xa0
  do_syscall_64+0xa6/0x1c0
  entry_SYSCALL64_slow_path+0x25/0x25
 ---[ end trace bd187ee0267df5d9 ]---

set downstream even with blacklist path.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 drivers/pci/pcie/aspm.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Index: linux-2.6/drivers/pci/pcie/aspm.c
===================================================================
--- linux-2.6.orig/drivers/pci/pcie/aspm.c
+++ linux-2.6/drivers/pci/pcie/aspm.c
@@ -478,7 +478,7 @@ static void aspm_calc_l1ss_info(struct p
 
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 {
-	struct pci_dev *child, *parent = link->pdev;
+	struct pci_dev *child = link->downstream, *parent = link->pdev;
 	struct pci_bus *linkbus = parent->subordinate;
 	struct aspm_register_info upreg, dwreg;
 
@@ -491,9 +491,7 @@ static void pcie_aspm_cap_init(struct pc
 
 	/* Get upstream/downstream components' register state */
 	pcie_get_aspm_reg(parent, &upreg);
-	child = pci_function_0(linkbus);
 	pcie_get_aspm_reg(child, &dwreg);
-	link->downstream = child;
 
 	/*
 	 * If ASPM not supported, don't mess with the clocks and link,
@@ -800,6 +798,7 @@ static struct pcie_link_state *alloc_pci
 	INIT_LIST_HEAD(&link->children);
 	INIT_LIST_HEAD(&link->link);
 	link->pdev = pdev;
+	link->downstream = pci_function_0(pdev->subordinate);
 
 	/*
 	 * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe