Hi,
On Thu, 2024-10-24 at 17:55 +0200, Takashi Iwai wrote:
> pcim_intx() tries to restore the INTX_DISABLE bit at removal via
> devres, but there is a chance that it restores a wrong value.
> Because the value to be restored is blindly assumed to be the
> negative
> of the enable argument, when a driver calls pcim_intx() unnecessarily
> for the already enabled state, it'll restore to the disabled state in
> turn.
It depends on how it is called, no?
// INTx == 1
pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> correct
---
// INTx == 0
pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> wrong
Maybe it makes sense to replace part of the commit text with something
like the example above?
> Also, when a driver calls pcim_intx() multiple times with
> different enable argument values, the last one will win no matter
> what
> value it is.
Means
// INTx == 0
pcim_intx(pdev, 0); // orig_INTx == 1, INTx == 0
pcim_intx(pdev, 1); // orig_INTx == 0, INTx == 1
pcim_intx(pdev, 0); // orig_INTx == 1, INTx == 0
So in this example the first call would cause a wrong orig_INTx, but
the last call – the one "who will win" – seems to do the right thing,
dosen't it?
>
> This patch addresses those inconsistencies by saving the original
> INTX_DISABLE state at the first devres_alloc(); this assures that the
> original state is restored properly, and the later pcim_intx() calls
> won't overwrite res->orig_intx any longer.
>
> Fixes: 25216afc9db5 ("PCI: Add managed pcim_intx()")
That commit is also in 6.11, so we need:
Cc: stable@xxxxxxxxxxxxxxx # 6.11+
> Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@xxxxxxx
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> ---
> drivers/pci/devres.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
> index b133967faef8..aed3c9a355cb 100644
> --- a/drivers/pci/devres.c
> +++ b/drivers/pci/devres.c
> @@ -438,8 +438,17 @@ static void pcim_intx_restore(struct device
> *dev, void *data)
> __pcim_intx(pdev, res->orig_intx);
> }
>
> -static struct pcim_intx_devres *get_or_create_intx_devres(struct
> device *dev)
> +static void save_orig_intx(struct pci_dev *pdev, struct
> pcim_intx_devres *res)
> {
> + u16 pci_command;
> +
> + pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
> + res->orig_intx = !(pci_command & PCI_COMMAND_INTX_DISABLE);
> +}
> +
> +static struct pcim_intx_devres *get_or_create_intx_devres(struct
> pci_dev *pdev)
> +{
> + struct device *dev = &pdev->dev;
> struct pcim_intx_devres *res;
>
> res = devres_find(dev, pcim_intx_restore, NULL, NULL);
> @@ -447,8 +456,10 @@ static struct pcim_intx_devres
> *get_or_create_intx_devres(struct device *dev)
> return res;
>
> res = devres_alloc(pcim_intx_restore, sizeof(*res),
> GFP_KERNEL);
> - if (res)
> + if (res) {
> + save_orig_intx(pdev, res);
This is not the correct place – get_or_create_intx_devres() should get
the resource if it exists, or allocate it if it doesn't, but its
purpose is not to modify the resource.
> devres_add(dev, res);
> + }
>
> return res;
> }
> @@ -467,11 +478,10 @@ int pcim_intx(struct pci_dev *pdev, int enable)
> {
> struct pcim_intx_devres *res;
>
> - res = get_or_create_intx_devres(&pdev->dev);
> + res = get_or_create_intx_devres(pdev);
> if (!res)
> return -ENOMEM;
>
> - res->orig_intx = !enable;
Here is the right place to call save_orig_intx(). That way you also
won't need the new variable struct device *dev above :)
Thank you,
P.
> __pcim_intx(pdev, enable);
>
> return 0;
