On Mon, Jun 25, 2018 at 02:13:26PM +0100, Marc Zyngier wrote: > On 25/06/18 13:52, Mika Westerberg wrote: > > On Thu, Jun 21, 2018 at 05:47:15PM +0100, Marc Zyngier wrote: > >> Until recently, shpc_probe() would bail out pretty early in the > >> absence of the SHPC capability. A logic change in the way the > >> driver now checks that capability makes it go and probe the > >> firmware anyway, with ugly consequences if the system is not > >> ACPI based (my arm64 ThunderX is DT driven, and explodes in > >> a spectacular way after getting a NULL root bridge from the > >> non-existent ACPI tables...). > > > > Could you share log from the failure? I would like to understand a bit > > better where it crashes and why. > > Here you go: > > [ 12.330017] pcieport 0008:1f:00.0: enabling device (0506 -> 0507) > [ 12.336315] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058 > [ 12.345104] Mem abort info: > [ 12.347895] ESR = 0x96000004 > [ 12.350945] Exception class = DABT (current EL), IL = 32 bits > [ 12.356860] SET = 0, FnV = 0 > [ 12.359910] EA = 0, S1PTW = 0 > [ 12.363046] Data abort info: > [ 12.365922] ISV = 0, ISS = 0x00000004 > [ 12.369748] CM = 0, WnR = 0 > [ 12.372712] [0000000000000058] user address but active_mm is swapper > [ 12.379063] Internal error: Oops: 96000004 [#1] PREEMPT SMP > [ 12.384625] Modules linked in: > [ 12.387676] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 4.18.0-rc1-00006-ga2c5c6a64fb6 #10 > [ 12.395929] Hardware name: FOXCONN R2-1221R-A4/C2U4N_MB, BIOS G31FB18A 03/31/2017 > [ 12.403408] Workqueue: events work_for_cpu_fn > [ 12.407758] pstate: 60000005 (nZCv daif -PAN -UAO) > [ 12.412544] pc : acpi_get_hp_hw_control_from_firmware+0xa0/0x2b0 > [ 12.418541] lr : acpi_get_hp_hw_control_from_firmware+0xa0/0x2b0 > [ 12.424537] sp : ffff00000a613c60 > [ 12.427841] x29: ffff00000a613c60 x28: 0000000000000000 > [ 12.433147] x27: ffff800fbeb8d0b0 x26: ffff00000982a068 > [ 12.438453] x25: 0000000000000000 x24: ffff000009feb898 > [ 12.443759] x23: 0000000000000000 x22: ffff000009808000 > [ 12.449064] x21: ffff0000098dee98 x20: ffff810fa60d9000 > [ 12.454370] x19: 0000000000000000 x18: ffffffffffffffff > [ 12.459675] x17: 0000000000000e00 x16: 0000000000000020 > [ 12.464981] x15: ffff000009808648 x14: ffff000089a31b8f > [ 12.470286] x13: 0000000000000000 x12: 0000000000000040 > [ 12.475591] x11: 000000000000004c x10: 0000000000000a20 > [ 12.480897] x9 : ffff00000a613d30 x8 : 0000000000000000 > [ 12.486202] x7 : ffff000009808648 x6 : 0000000000000057 > [ 12.491508] x5 : 0000000000000010 x4 : 000000000000001f > [ 12.496813] x3 : 0000000000000000 x2 : 0d68a3f9b2251000 > [ 12.502118] x1 : 0000000000000000 x0 : 0000000000000000 > [ 12.507425] Process kworker/0:0 (pid: 5, stack limit = 0x(____ptrval____)) > [ 12.514289] Call trace: > [ 12.516727] acpi_get_hp_hw_control_from_firmware+0xa0/0x2b0 > [ 12.522377] shpc_probe+0x48/0x3b0 > [ 12.525772] local_pci_probe+0x44/0xb0 > [ 12.529511] work_for_cpu_fn+0x20/0x30 > [ 12.533252] process_one_work+0x208/0x480 > [ 12.537251] worker_thread+0x254/0x448 > [ 12.540992] kthread+0x104/0x130 > [ 12.544212] ret_from_fork+0x10/0x1c > [ 12.547779] Code: f100427f 54000040 f85f8260 94009f63 (b9405800) > [ 12.553866] ---[ end trace 8ee5b8cc95cd4f02 ]--- > > >> Take this opportunity to move the call to shpchp_is_native() > >> back into shpc_probe(), making it clear that a non-ACPI system > >> is not expected to use this driver. > > > > It is fine to use SHPC in non-ACPI systems. However, in ACPI systems we > > should negotiate whether it is the OS or the firmware who handles it. > Fair enough. In which case we should at the very least make sure > we can handle acpi_pci_find_root() returning NULL (which is what > generates the crash in my case). Agreed. Can you try if the below patch fixes the issue for you? diff --git a/drivers/pci/hotplug/acpi_pcihp.c b/drivers/pci/hotplug/acpi_pcihp.c index 3979f89b250a..73bc92cf0594 100644 --- a/drivers/pci/hotplug/acpi_pcihp.c +++ b/drivers/pci/hotplug/acpi_pcihp.c @@ -88,6 +88,9 @@ int acpi_get_hp_hw_control_from_firmware(struct pci_dev *pdev) /* If _OSC exists, we should not evaluate OSHP */ host = pci_find_host_bridge(pdev->bus); + if (!ACPI_HANDLE(&host->dev)) + return 0; + root = acpi_pci_find_root(ACPI_HANDLE(&host->dev)); if (root->osc_support_set) goto no_control;
