Re: [PATCH V10 4/4] PCI: vmd: Add quirk to configure PCIe ASPM and LTR

Ville Syrjälä
2023-03-20T22:56:45Z

On Thu, Jan 19, 2023 at 07:15:22PM -0800, David E. Box wrote:
> +/*
> + * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
> + */
> +static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> +{
> + unsigned long features = *(unsigned long *)userdata;
> + u16 ltr = VMD_BIOS_PM_QUIRK_LTR;
> + u32 ltr_reg;
> + int pos;
> +
> + if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> + return 0;
> +
> + pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);

Hi,

This is tripping lockdep on one our CI ADL machines.

https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_12814/bat-adlp-6/boot0.txt

<4>[ 13.815380] ============================================
<4>[ 13.815382] WARNING: possible recursive locking detected
<4>[ 13.815384] 6.3.0-rc1-CI_DRM_12814-g4753bbc2a817+ #1 Not tainted
<4>[ 13.815386] --------------------------------------------
<4>[ 13.815387] swapper/0/1 is trying to acquire lock:
<4>[ 13.815389] ffffffff827ab0b0 (pci_bus_sem){++++}-{3:3}, at: pci_enable_link_state+0x69/0x1d0
<4>[ 13.815396]
but task is already holding lock:
<4>[ 13.815398] ffffffff827ab0b0 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x24/0x90
<4>[ 13.815403]
other info that might help us debug this:
<4>[ 13.815404] Possible unsafe locking scenario:

<4>[ 13.815406] CPU0
<4>[ 13.815407] ----
<4>[ 13.815408] lock(pci_bus_sem);
<4>[ 13.815410] lock(pci_bus_sem);
<4>[ 13.815411]
*** DEADLOCK ***

<4>[ 13.815413] May be due to missing lock nesting notation

<4>[ 13.815414] 2 locks held by swapper/0/1:
<4>[ 13.815416] #0: ffff8881029511b8 (&dev->mutex){....}-{3:3}, at: __driver_attach+0xab/0x180
<4>[ 13.815422] #1: ffffffff827ab0b0 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x24/0x90
<4>[ 13.815426]
stack backtrace:
<4>[ 13.815428] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc1-CI_DRM_12814-g4753bbc2a817+ #1
<4>[ 13.815431] Hardware name: Intel Corporation Alder Lake Client Platform/AlderLake-P DDR4 RVP, BIOS ADLPFWI1.R00.3135.A00.2203251419 03/25/2022
<4>[ 13.815434] Call Trace:
<4>[ 13.815436] <TASK>
<4>[ 13.815437] dump_stack_lvl+0x64/0xb0
<4>[ 13.815443] __lock_acquire+0x9b5/0x2550
<4>[ 13.815461] lock_acquire+0xd7/0x330
<4>[ 13.815463] ? pci_enable_link_state+0x69/0x1d0
<4>[ 13.815466] down_read+0x3d/0x180
<4>[ 13.815480] ? pci_enable_link_state+0x69/0x1d0
<4>[ 13.815482] pci_enable_link_state+0x69/0x1d0
<4>[ 13.815485] ? __pfx_vmd_pm_enable_quirk+0x10/0x10
<4>[ 13.815488] vmd_pm_enable_quirk+0x49/0xb0
<4>[ 13.815490] pci_walk_bus+0x6d/0x90
<4>[ 13.815492] vmd_probe+0x75f/0x9d0
<4>[ 13.815495] pci_device_probe+0x95/0x120
<4>[ 13.815498] really_probe+0x164/0x3c0
<4>[ 13.815500] ? __pfx___driver_attach+0x10/0x10
<4>[ 13.815503] __driver_probe_device+0x73/0x170
<4>[ 13.815506] driver_probe_device+0x19/0xa0
<4>[ 13.815508] __driver_attach+0xb6/0x180
<4>[ 13.815511] ? __pfx___driver_attach+0x10/0x10
<4>[ 13.815513] bus_for_each_dev+0x77/0xd0
<4>[ 13.815516] bus_add_driver+0x114/0x210
<4>[ 13.815518] driver_register+0x5b/0x110
<4>[ 13.815520] ? __pfx_vmd_drv_init+0x10/0x10
<4>[ 13.815523] do_one_initcall+0x57/0x330
<4>[ 13.815527] kernel_init_freeable+0x181/0x3a0
<4>[ 13.815529] ? __pfx_kernel_init+0x10/0x10
<4>[ 13.815532] kernel_init+0x15/0x120
<4>[ 13.815534] ret_from_fork+0x29/0x50
<4>[ 13.815537] </TASK>

--
Ville Syrjälä
Intel