linux-kernel - Re: [PATCH] PCI: Remove usage of pci_domain

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Message-ID: <20160225151040.GB23155@localhost>
Date:	Thu, 25 Feb 2016 09:10:40 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	jakeo@...rosoft.com
Cc:	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	gregkh@...uxfoundation.org, kys@...rosoft.com,
	linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
	olaf@...fle.de, apw@...onical.com, vkuznets@...hat.com,
	tglx@...utronix.de, haiyangz@...rosoft.com, marc.zyngier@....com,
	haddenh@...rosoft.com
Subject: Re: [PATCH] PCI: Remove usage of pci_domain_nr when the PCI bus
 doesn't yet exist

On Wed, Feb 24, 2016 at 06:56:36PM +0000, jakeo@...rosoft.com wrote:
> From: Jake Oshins <jakeo@...rosoft.com>
> 
> This patch fixes a race condition in this driver.  Using the
> function pci_domain_nr() only works if the PCI bus has already
> been fully created.  This patch just deletes one call site,
> as it was in debug prints which aren't strictly necessary.
> Another call site is changed to look for the data in the same
> structure that is passed in when creating the PCI bus in the
> first place.
> 
> Signed-off-by: Jake Oshins <jakeo@...rosoft.com>

I folded this into the original "Add paravirtual PCI front-end for
Microsoft Hyper-V VMs" patch and updated the pci/host-hv branch.

Thanks, Jake!

> ---
>  drivers/pci/host/pci-hyperv.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 9391dee..ed651ba 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1265,11 +1265,6 @@ static struct hv_pci_dev *new_pcichild_device(struct hv_pcibus_device *hbus,
>  	if (!hpdev)
>  		return NULL;
>  
> -	dev_info(&hbus->hdev->device,
> -		 "New child device (%p) [%04x:%04x] at %04x:00:00.%02x\n",
> -		 hpdev, desc->v_id, desc->d_id, pci_domain_nr(hbus->pci_bus),
> -		 desc->win_slot.bits.func);
> -
>  	hpdev->hbus = hbus;
>  
>  	memset(&pkt, 0, sizeof(pkt));
> @@ -1558,9 +1553,15 @@ static void hv_eject_device_work(struct work_struct *work)
>  		return;
>  	}
>  
> +	/*
> +	 * Ejection can come before or after the PCI bus has been set up, so
> +	 * attempt to find it and tear down the bus state, if it exists.  This
> +	 * must be done without constructs like pci_domain_nr(hbus->pci_bus)
> +	 * because hbus->pci_bus may not exist yet.
> +	 */
>  	wslot = wslot_to_devfn(hpdev->desc.win_slot.slot);
> -	pdev = pci_get_domain_bus_and_slot(pci_domain_nr(hpdev->hbus->pci_bus),
> -					   0, wslot);
> +	pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
> +					   wslot);
>  	if (pdev) {
>  		pci_stop_and_remove_bus_device(pdev);
>  		pci_dev_put(pdev);
> -- 
> 1.9.1
> 
> --
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