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SubjectRe: [PATCH] x86/PCI: Fully disable devices before releasing IRQ resource
On 2015/3/6 5:06, Alex Williamson wrote:
> The IRQ resource for a device is established when pci_enabled_device()
> is called on a fully disabled device (ie. enable_cnt == 0). With
> commit b4b55cda5874 ("x86/PCI: Refine the way to release PCI IRQ
> resources") this same IRQ resource is released when the driver is
> unbound from the device, regardless of the enable_cnt. This presents
> the situation that an ill-behaved driver can now make a device
> unusable to subsequent drivers by an imbalance in their use of
> pci_enable/disable_device(). It's one thing to break your own device
> if you're one of these ill-behaved drivers, but it's a serious
> regression for secondary drivers like vfio-pci, which are innocent
> of the transgressions of the previous driver.
>
> Resolve by pushing the device to a fully disabled state before
> releasing the IRQ resource.
>
> Fixes: b4b55cda5874 ("x86/PCI: Refine the way to release PCI IRQ resources")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Cc: Jiang Liu <jiang.liu@linux.intel.com>
> ---
> arch/x86/pci/common.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 3d2612b..4810194 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -527,8 +527,19 @@ static int pci_irq_notifier(struct notifier_block *nb, unsigned long action,
> if (action != BUS_NOTIFY_UNBOUND_DRIVER)
> return NOTIFY_DONE;
>
> - if (pcibios_disable_irq)
> + if (pcibios_disable_irq) {
> + /*
> + * Broken drivers may allow a device to be .remove()'d while
> + * still enabled. pci_enable_device() will only re-establish
> + * dev->irq if the devices is fully disabled. So if we want
> + * to release the IRQ, we need to make sure the next driver
> + * can re-establish it using pci_enable_device().
> + */
> + while (pci_is_enabled(dev))
> + pci_disable_device(dev);
> +
> pcibios_disable_irq(dev);
> + }
Hi Alex,
Thanks for debugging and fixing it.
Will it be feasible to give a debug message to remind those
driver authors to correctly disable PCI when unbinding?
Regards!
Gerry

>
> return NOTIFY_OK;
> }
>


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