From 1469d17dd341458267a08c8d8bb517cb986ec56d Mon Sep 17 00:00:00 2001 From: Jarod Wilson Date: Tue, 21 Jul 2015 12:25:30 -0400 Subject: [PATCH] PCI: pciehp: Handle invalid data when reading from non-existent devices It's platform-dependent, but an MMIO read to a non-existent PCI device generally returns data with all bits set. This happens when the host bridge or Root Complex times out waiting for a response from the device and fabricates return data to complete the CPU's read. One example, reported in the bugzilla below, involved this hierarchy: pci 0000:00:1c.0: PCI bridge to [bus 02-3a] Root Port pci 0000:02:00.0: PCI bridge to [bus 03-0a] Upstream Port pci 0000:03:03.0: PCI bridge to [bus 05-07] Downstream Port pci 0000:05:00.0: PCI bridge to [bus 06-07] Thunderbolt Upstream Port pci 0000:06:00.0: PCI bridge to [bus 07] Thunderbolt Downstream Port pci 0000:07:00.0: BCM57762 NIC Unplugging the Thunderbolt switch and the NIC below it resulted in this: pciehp 0000:03:03.0: Surprise Removal tg3 0000:07:00.0: tg3_abort_hw timed out, TX_MODE_ENABLE will not clear MAC_TX_MODE=ffffffff pciehp 0000:06:00.0: unloading service driver pciehp pciehp 0000:06:00.0: pcie_isr: intr_loc 11f pciehp 0000:06:00.0: Switch interrupt received pciehp 0000:06:00.0: Latch open on Slot pciehp 0000:06:00.0: Attention button interrupt received pciehp 0000:06:00.0: Button pressed on Slot pciehp 0000:06:00.0: Presence/Notify input change pciehp 0000:06:00.0: Card present on Slot pciehp 0000:06:00.0: Power fault interrupt received pciehp 0000:06:00.0: Data Link Layer State change pciehp 0000:06:00.0: Link Up event The pciehp driver correctly noticed that the Thunderbolt switch (05:00.0 and 06:00.0) and NIC (07:00.0) had been removed, and it called their driver remove methods. Since the NIC was already gone, tg3 received 0xffffffff when it tried to read from the device. The resulting timeout is a tg3 issue and not of interest here. Similarly, since the 06:00.0 Thunderbolt switch was already gone, pcie_isr() received 0xffff when it tried to read PCI_EXP_SLTSTA, and pciehp thought that was valid status showing that many events had happened: the latch had been opened, the attention button had been pressed, a card was now present, and the link was now up. These are all wrong, of course, but pciehp went on to try to power up and enumerate devices below the non-existent bridge: pciehp 0000:06:00.0: PCI slot - powering on due to button press pciehp 0000:06:00.0: Surprise Insertion pci 0000:07:00.0 id reading try 50 times with interval 20 ms to get ffffffff [bhelgaas: changelog, also check in pcie_poll_cmd() & pcie_do_write_cmd()] Link: https://bugzilla.kernel.org/show_bug.cgi?id=99841 Suggested-by: Bjorn Helgaas Signed-off-by: Jarod Wilson Signed-off-by: Bjorn Helgaas --- drivers/pci/hotplug/pciehp_hpc.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index daf54bee720d..8f3d3cff3581 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -111,6 +111,12 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout) while (true) { pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); + if (slot_status == (u16) ~0) { + ctrl_info(ctrl, "%s: no response from device\n", + __func__); + return 0; + } + if (slot_status & PCI_EXP_SLTSTA_CC) { pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_CC); @@ -186,6 +192,11 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd, pcie_wait_cmd(ctrl); pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &slot_ctrl); + if (slot_ctrl == (u16) ~0) { + ctrl_info(ctrl, "%s: no response from device\n", __func__); + goto out; + } + slot_ctrl &= ~mask; slot_ctrl |= (cmd & mask); ctrl->cmd_busy = 1; @@ -201,6 +212,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd, if (wait) pcie_wait_cmd(ctrl); +out: mutex_unlock(&ctrl->ctrl_lock); } @@ -542,6 +554,11 @@ static irqreturn_t pcie_isr(int irq, void *dev_id) intr_loc = 0; do { pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &detected); + if (detected == (u16) ~0) { + ctrl_info(ctrl, "%s: no response from device\n", + __func__); + return IRQ_HANDLED; + } detected &= (PCI_EXP_SLTSTA_ABP | PCI_EXP_SLTSTA_PFD | PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_PDC | -- 2.20.1