linux-kernel - Re: [PATCH 1/2 v4] pci-hyperv: properly handle pci bus remove

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Message-ID: <20170316200658.GC9739@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 16 Mar 2017 15:06:58 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Long Li <longli@...rosoft.com>
Cc:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v4] pci-hyperv: properly handle pci bus remove

On Tue, Feb 28, 2017 at 02:19:45AM +0000, Long Li wrote:
> hv_pci_devices_present is called in hv_pci_remove when we remove a PCI
> device from host (e.g. by disabling SRIOV on a device). In hv_pci_remove,
> the bus is already removed before the call, so we don't need to rescan 
> the bus in the workqueue scheduled from hv_pci_devices_present. By 
> introducing status hv_pcibus_removed, we can avoid this situation.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> Reported-by: Xiaofeng Wang <xiaofwan@...hat.com>
> Acked-by: K. Y. Srinivasan <kys@...rosoft.com>

This didn't apply for me because saving it to a file resulted in some
encoded file with "=3D" instead of "=".  I see that mutt is smart enough to
deal with that in this reply, so there's probably a way for it to decode it
when saving to a file, but I don't know it.

I tried to apply it by hand, but the hunk in hv_pci_remove() doesn't match
the context.  I think your patch is based on something previous to
17978524a636 ("PCI: hv: Fix hv_pci_remove() for hot-remove").  Please
refresh the patch so it applies to my "master" branch (currently
v4.11-rc1).

Also, the "default: break;" case below is redundant and can be removed.

So I'll wait for your updated versions of both these patches.

> ---
>  drivers/pci/host/pci-hyperv.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index a8deeca..4a37598 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -348,6 +348,7 @@ enum hv_pcibus_state {
>  	hv_pcibus_init = 0,
>  	hv_pcibus_probed,
>  	hv_pcibus_installed,
> +	hv_pcibus_removed,
>  	hv_pcibus_maximum
>  };
>  
> @@ -1481,13 +1482,24 @@ static void pci_devices_present_work(struct work_struct *work)
>  		put_pcichild(hpdev, hv_pcidev_ref_initial);
>  	}
>  
> -	/* Tell the core to rescan bus because there may have been changes. */
> -	if (hbus->state == hv_pcibus_installed) {
> +	switch (hbus->state) {
> +	case hv_pcibus_installed:
> +		/*
> +		 * Tell the core to rescan bus
> +		 * because there may have been changes.
> +		 */
>  		pci_lock_rescan_remove();
>  		pci_scan_child_bus(hbus->pci_bus);
>  		pci_unlock_rescan_remove();
> -	} else {
> +		break;
> +
> +	case hv_pcibus_init:
> +	case hv_pcibus_probed:
>  		survey_child_resources(hbus);
> +		break;
> +
> +	default:
> +		break;

^ This is redundant.

>  	}
>  
>  	up(&hbus->enum_sem);
> @@ -2163,6 +2175,7 @@ static int hv_pci_probe(struct hv_device *hdev,
>  	hbus = kzalloc(sizeof(*hbus), GFP_KERNEL);
>  	if (!hbus)
>  		return -ENOMEM;
> +	hbus->state = hv_pcibus_init;
>  
>  	/*
>  	 * The PCI bus "domain" is what is called "segment" in ACPI and
> @@ -2305,6 +2318,7 @@ static int hv_pci_remove(struct hv_device *hdev)
>  		pci_stop_root_bus(hbus->pci_bus);
>  		pci_remove_root_bus(hbus->pci_bus);
>  		pci_unlock_rescan_remove();
> +		hbus->state = hv_pcibus_removed;
>  	}
>  
>  	ret = hv_send_resources_released(hdev);
> -- 
> 1.8.5.6