Subject: Re: [PATCH RFC v4 03/21] PCI: Enable bridge's I/O and MEM access for hotplugged devices

From: Bjorn Helgaas <[email-masked]>
Date: Tue, 26 Mar 2019 14:13:07 -0500

On Mon, Mar 11, 2019 at 04:31:04PM +0300, Sergey Miroshnichenko wrote:
> After updating the bridge window resources, the PCI_COMMAND_IO and
> PCI_COMMAND_MEMORY bits of the bridge must be addressed as well.
> 
> Signed-off-by: Sergey Miroshnichenko <[email-masked]>
> ---
>  drivers/pci/pci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 895201d4c9e6..69898fe5255e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1622,6 +1622,14 @@ static void pci_enable_bridge(struct pci_dev *dev)
>  		pci_enable_bridge(bridge);
>  
>  	if (pci_is_enabled(dev)) {
> +		int i, bars = 0;
> +
> +		for (i = PCI_BRIDGE_RESOURCES; i < DEVICE_COUNT_RESOURCE; i++) {
> +			if (dev->resource[i].flags & (IORESOURCE_MEM | IORESOURCE_IO))
> +				bars |= (1 << i);
> +		}
> +		do_pci_enable_device(dev, bars);

In what situation is this needed, exactly?  This code already exists
in pci_enable_device_flags().  Why isn't that enough?

I guess maybe there's some case where we enable the bridge, then
assign bridge windows, then enable a downstream device?

Does this fix a bug with current hotplug?

>  		if (!dev->is_busmaster)
>  			pci_set_master(dev);
>  		mutex_unlock(&dev->enable_mutex);
> -- 
> 2.20.1
>