Re: [PATCH] PCI: Remove usage of pci_domain_nr when the PCI bus doesn't yet exist

From: Bjorn Helgaas
Date: Thu Feb 25 2016 - 10:10:55 EST


On Wed, Feb 24, 2016 at 06:56:36PM +0000, jakeo@xxxxxxxxxxxxx wrote:
> From: Jake Oshins <jakeo@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>

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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