Re: [PATCH v9 10/13] PCI: Give pci_intx() its own devres callback

Kalra, Ashish
2024-07-09T18:46:29Z

Hello Philipp,

I have reviewed and tested this patch, looks to be working fine and fixes the issue.

Thanks, Ashish

On 7/9/2024 3:56 AM, Philipp Stanner wrote:
> From c24bd5b66e798a341caf183fb7cdbdf235502d90 Mon Sep 17 00:00:00 2001
> From: Philipp Stanner <pstanner@redhat.com>
> Date: Tue, 9 Jul 2024 09:45:48 +0200
> Subject: [PATCH] PCI: Fix pcim_intx() recursive calls
>
> pci_intx() calls into pcim_intx() in managed mode, i.e., when
> pcim_enable_device() had been called. This recursive call causes a bug
> by re-registering the device resource in the release callback.
>
> This is the same phenomenon that made it necessary to implement some
> functionality a second time, see __pcim_request_region().
>
> Implement __pcim_intx() to bypass the hybrid nature of pci_intx() on
> driver detach.
>
> Fixes: https://lore.kernel.org/all/20240708214656.4721-1-Ashish.Kalra@amd.com/
> Reported-by: Ashish Kalra <Ashish.Kalra@amd.com>
> Signed-off-by: Philipp Stanner <pstanner@redhat.com>
> ---
> Hi Ashish,
> I hacked down this fix that should be applyable on top.
> Could you maybe have a first quick look whether this fixes the issue?
> ---
> drivers/pci/devres.c | 33 +++++++++++++++++++++------------
> 1 file changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
> index 2f0379a4e58f..dcef049b72fe 100644
> --- a/drivers/pci/devres.c
> +++ b/drivers/pci/devres.c
> @@ -408,12 +408,31 @@ static inline bool mask_contains_bar(int mask, int bar)
> return mask & BIT(bar);
> }
>
> +/*
> + * This is a copy of pci_intx() used to bypass the problem of occuring
> + * recursive function calls due to the hybrid nature of pci_intx().
> + */
> +static void __pcim_intx(struct pci_dev *pdev, int enable)
> +{
> + u16 pci_command, new;
> +
> + pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
> +
> + if (enable)
> + new = pci_command & ~PCI_COMMAND_INTX_DISABLE;
> + else
> + new = pci_command | PCI_COMMAND_INTX_DISABLE;
> +
> + if (new != pci_command)
> + pci_write_config_word(pdev, PCI_COMMAND, new);
> +}
> +
> static void pcim_intx_restore(struct device *dev, void *data)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> struct pcim_intx_devres *res = data;
>
> - pci_intx(pdev, res->orig_intx);
> + __pcim_intx(pdev, res->orig_intx);
> }
>
> static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
> @@ -443,7 +462,6 @@ static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev)
> */
> int pcim_intx(struct pci_dev *pdev, int enable)
> {
> - u16 pci_command, new;
> struct pcim_intx_devres *res;
>
> res = get_or_create_intx_devres(&pdev->dev);
> @@ -451,16 +469,7 @@ int pcim_intx(struct pci_dev *pdev, int enable)
> return -ENOMEM;
>
> res->orig_intx = !enable;
> -
> - pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
> -
> - if (enable)
> - new = pci_command & ~PCI_COMMAND_INTX_DISABLE;
> - else
> - new = pci_command | PCI_COMMAND_INTX_DISABLE;
> -
> - if (new != pci_command)
> - pci_write_config_word(pdev, PCI_COMMAND, new);
> + __pcim_intx(pdev, enable);
>
> return 0;
> }
Tested-by: Ashish Kalra <Ashish.Kalra@amd.com>