Re: [PATCH 2/6] PCI: vmd: Fix deadlock when enabling ASPM

Manivannan Sadhasivam
2023-11-17T10:28:53Z

On Tue, Nov 14, 2023 at 02:55:49PM +0100, Johan Hovold wrote:
> The vmd_pm_enable_quirk() helper is called from pci_walk_bus() during
> probe to enable ASPM for controllers with VMD_FEAT_BIOS_PM_QUIRK set.
>
> Since pci_walk_bus() already holds a pci_bus_sem read lock, use the new
> locked helper to enable link states in order to avoid a potential
> deadlock (e.g. in case someone takes a write lock before reacquiring
> the read lock).
>
> Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
> Cc: stable@vger.kernel.org # 6.3
> Cc: Michael Bottini <michael.a.bottini@linux.intel.com>
> Cc: David E. Box <david.e.box@linux.intel.com>
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
> drivers/pci/controller/vmd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 94ba61fe1c44..0452cbc362ee 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -751,7 +751,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> return 0;
>
> - pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
> + pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
>
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> if (!pos)
> --
> 2.41.0
>

--
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