On Tue, Sep 27, 2016 at 04:23:32PM -0400, Keith Busch wrote:
> This adds a new state for devices that were once in the system, but
> unexpectedly removed. This is so device tear down functions can observe
> the device is not accessible so it may skip attempting to initialize
> the hardware.
[...]
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -337,6 +337,7 @@ struct pci_dev {
> unsigned int multifunction:1;/* Part of multi-function device */
> /* keep track of device state */
> unsigned int is_added:1;
> + unsigned int is_removed:1; /* device was surprise removed */
> unsigned int is_busmaster:1; /* device is busmaster */
> unsigned int no_msi:1; /* device may not use msi */
> unsigned int no_64bit_msi:1; /* device may only use 32-bit MSIs */
The tg3 driver (as well as many other drivers) already check reachability
of a device before accessing its mmio space by calling pci_channel_offline().
I've found that the following simple change on top of your series is
already sufficient to make hot-removal of the Apple Gigabit Ethernet
adapter "just work" (no more soft lockups, which is a giant improvement):
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5c43012..cc8b234 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -406,7 +406,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus);
static inline int pci_channel_offline(struct pci_dev *pdev)
{
- return (pdev->error_state != pci_channel_io_normal);
+ return pdev->error_state != pci_channel_io_normal || pdev->is_removed;
}
struct pci_host_bridge {
This got me thinking: We've got three pci_channel_state values defined
in include/linux/pci.h, "normal", "frozen" and "perm_failure". Instead
of adding a new "is_removed" bit to struct pci_dev, would it perhaps
make more sense to just add a new type of pci_channel_state for removed
devices? Then the above change to pci_channel_offline() wouldn't even
be necessary. The pciehp and dpc drivers would just change the channel
status to "removed" and all the drivers already querying it with
pci_channel_offline() would pick up the change automatically.
Thoughts?
Thanks,
Lukas
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