Commit d555ed45 authored by Takashi Iwai's avatar Takashi Iwai Committed by Bjorn Helgaas
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PCI: Restore original INTX_DISABLE bit by pcim_intx() 

pcim_intx() tries to restore the INTx 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.  That
is, the function assumes the case like:

  // INTx == 1
  pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> correct

but it might be like the following, too:

  // INTx == 0
  pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> wrong

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.  This
can lead to inconsistency, e.g.

  // INTx == 1
  pcim_intx(pdev, 0); // OK
  ...
  pcim_intx(pdev, 1); // now old INTx wrongly assumed to be 0

This patch addresses those inconsistencies by saving the original INTx
state at the first pcim_intx() call.  For that, get_or_create_intx_devres()
is folded into pcim_intx() caller side; it allows us to simply check the
already allocated devres and record the original INTx along with the
devres_alloc() call.

Link: https://lore.kernel.org/r/20241031134300.10296-1-tiwai@suse.de
Fixes: 25216afc ("PCI: Add managed pcim_intx()")
Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarPhilipp Stanner <pstanner@redhat.com>
Cc: stable@vger.kernel.org	# v6.11+
parent 647d6960

drivers/pci/devres.c

+19 −15
Original line number Diff line number Diff line
@@ -419,19 +419,12 @@ static void pcim_intx_restore(struct device *dev, void *data) 
	pci_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)

{

	struct pcim_intx_devres *res;



	res = devres_find(dev, pcim_intx_restore, NULL, NULL);

	if (res)

		return res;



	res = devres_alloc(pcim_intx_restore, sizeof(*res), GFP_KERNEL);

	if (res)

		devres_add(dev, res);

	u16 pci_command;



	return res;

	pci_read_config_word(pdev, PCI_COMMAND, &pci_command);

	res->orig_intx = !(pci_command & PCI_COMMAND_INTX_DISABLE);

}



/**
@@ -447,12 +440,23 @@ static struct pcim_intx_devres *get_or_create_intx_devres(struct device *dev) 
int pcim_intx(struct pci_dev *pdev, int enable)

{

	struct pcim_intx_devres *res;

	struct device *dev = &pdev->dev;



	res = get_or_create_intx_devres(&pdev->dev);

	/*

	 * pcim_intx() must only restore the INTx value that existed before the

	 * driver was loaded, i.e., before it called pcim_intx() for the

	 * first time.

	 */

	res = devres_find(dev, pcim_intx_restore, NULL, NULL);

	if (!res) {

		res = devres_alloc(pcim_intx_restore, sizeof(*res), GFP_KERNEL);

		if (!res)

			return -ENOMEM;



	res->orig_intx = !enable;

		save_orig_intx(pdev, res);

		devres_add(dev, res);

	}



	pci_intx(pdev, enable);



	return 0;