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From:   Michael Kelley <mikelley@microsoft.com>
To:     "longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <sashal@kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Andrew Murray <andrew.murray@arm.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Dexuan Cui <decui@microsoft.com>
CC:     Long Li <longli@microsoft.com>
Subject: RE: [EXTERNAL] [PATCH 2/2] PCI: hv: Add support for protocol 1.3 and
 support PCI_BUS_RELATIONS2
Thread-Topic: [EXTERNAL] [PATCH 2/2] PCI: hv: Add support for protocol 1.3 and
 support PCI_BUS_RELATIONS2
Thread-Index: AQHVoaFeiJWyuTLLsUiMTX6LeRJTSaejKm4Q
Date:   Sat, 30 Nov 2019 04:45:36 +0000
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 <1574474229-44840-2-git-send-email-longli@linuxonhyperv.com>
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From: longli@linuxonhyperv.com Sent: Friday, November 22, 2019 5:57 PM
>=20
> From: Long Li <longli@microsoft.com>
>=20
> Starting with Hyper-V PCI protocol version 1.3, the host VSP can send
> PCI_BUS_RELATIONS2 and pass the vNUMA node information for devices on the=
 bus.
> The vNUMA node tells which guest NUMA node this device is on based on gue=
st
> VM configuration topology and physical device inforamtion.
>=20
> The patch adds code to negotiate v1.3 and process PCI_BUS_RELATIONS2.
>=20
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/pci/controller/pci-hyperv.c | 107 ++++++++++++++++++++++++++++
>  1 file changed, 107 insertions(+)
>=20

[snip]

> +/*
> + * Set NUMA node for the devices on the bus
> + */
> +static void pci_assign_numa_node(struct hv_pcibus_device *hbus)
> +{
> +	struct pci_dev *dev;
> +	struct pci_bus *bus =3D hbus->pci_bus;
> +	struct hv_pci_dev *hv_dev;
> +
> +	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		hv_dev =3D get_pcichild_wslot(hbus, devfn_to_wslot(dev->devfn));
> +		if (!hv_dev)
> +			continue;
> +
> +		if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY)
> +			set_dev_node(&dev->dev, hv_dev->desc.virtual_numa_node);
> +	}
> +}
> +

get_pcichild_wslot() gets a reference to the hv_dev, so a call to put_pcich=
ild() is
needed to balance.

But more broadly, is the call to set_dev_node() operating on the correct
struct device?  There's a struct device in the struct hv_device, and also o=
ne in the
struct pci_dev.  Everything in this module seems to be operating on the for=
mer.
For example, all the dev_err() calls identify the struct device in struct h=
v_device.
And enumerating all the devices on a virtual PCI bus is done by iterating t=
hrough
the hbus->children list, not the bus->devices list.  I don't completely und=
erstand
the interplay between the two struct device entries, but the difference mak=
es
me wonder if the above code should be setting the NUMA node on the struct
device that's in struct hv_device.

Michael