linux-kernel - Re: [PATCH v5] PCI: hv: Make sure the bus domain is really unique

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Date:   Fri, 30 Mar 2018 19:35:04 +0000
From:   Sridhar Pitchai <Sridhar.Pitchai@...rosoft.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Jake Oshins <jakeo@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.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 v5] PCI: hv: Make sure the bus domain is really unique

  >When Linux runs as a guest VM in Hyper-V and Hyper-V adds the virtual
  >PCI bus to the guest, Hyper-V always provides unique PCI domain.
  >
  >commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI domain")
  >overrode unique domain with the serial number of the first device added
  >to the virtual PCI bus. The reason for that patch is to have a consistent
  >and short name for the device. But commit 4a9b0933bdfc ("PCI: hv: Use
  >device serial number as PCI domain") will not guarantee unique domain id.
  >For example, if the serial number of the device is 0 and there exists a
  >PCI bus with domain 0 already, this will cause the PCI bus registration
  >with kernel fails.
  >
  >commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI
  >domain") need to be reverted. Also, we no longer need it as commit
  >4a1626dd233e ("netvsc: transparent VF management") remove the
  >need for it.
  >
  >Revert commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI
  >domain") so we can reliably support multiple devices being assigned to
  >a guest.
  >
  >This revert should only be backported to kernels that contain commit
  >4a1626dd233e ("netvsc: transparent VF management").
  >
  >Fixes: 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI domain")
  >Signed-off-by: Sridhar Pitchai <sridhar.pitchai@...rosoft.com>
  >Cc: stable@...r.kernel.org
  >
  >---
  >Changes in v5:
  >* fix the commit comment. [Lorenzo Pieralisi, Bjorn Helgaas]
  >* fixed the patch white space.
  >---
  > drivers/pci/host/pci-hyperv.c | 11 -----------
  > 1 file changed, 11 deletions(-)
  >
  >diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
  >index 2faf38eab785..ac67e56e451a 100644
  >--- a/drivers/pci/host/pci-hyperv.c
  >+++ b/drivers/pci/host/pci-hyperv.c
  >@@ -1518,17 +1518,6 @@ static struct hv_pci_dev *new_pcichild_device(struct hv_pcibus_device *hbus,
  > 	get_pcichild(hpdev, hv_pcidev_ref_childlist);
  > 	spin_lock_irqsave(&hbus->device_list_lock, flags);
  > 
  >-	/*
  >-	 * When a device is being added to the bus, we set the PCI domain
  >-	 * number to be the device serial number, which is non-zero and
  >-	 * unique on the same VM.  The serial numbers start with 1, and
  >-	 * increase by 1 for each device.  So device names including this
  >-	 * can have shorter names than based on the bus instance UUID.
  >-	 * Only the first device serial number is used for domain, so the
  >-	 * domain number will not change after the first device is added.
  >-	 */
  >-	if (list_empty(&hbus->children))
  >-		hbus->sysdata.domain = desc->ser;
  > 	list_add_tail(&hpdev->list_entry, &hbus->children);
  > 	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
  > 	return hpdev;
  >-- 
>2.14.1

Hi Lorenzo,
Did you get a chance to look at the patch v5. Please let me know if
anything I need to address further.

Thanks
Sridhar