linux-kernel - RE: [EXTERNAL] [PATCH 2/2] PCI: hv: Add support for protocol 1.3 and support PCI_BUS

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Message-ID: <PU1P153MB0169CFE46920BAEEE11CA9B7BF430@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Mon, 2 Dec 2019 23:59:09 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "longli@...uxonhyperv.com" <longli@...uxonhyperv.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <andrew.murray@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Long Li <longli@...rosoft.com>
Subject: RE: [EXTERNAL] [PATCH 2/2] PCI: hv: Add support for protocol 1.3 and
 support PCI_BUS_RELATIONS2

> From: linux-hyperv-owner@...r.kernel.org
> Sent: Friday, November 22, 2019 5:57 PM
>  ...
> @@ -63,6 +63,7 @@
>  enum pci_protocol_version_t {
>  	PCI_PROTOCOL_VERSION_1_1 = PCI_MAKE_VERSION(1, 1),	/* Win10
> */
>  	PCI_PROTOCOL_VERSION_1_2 = PCI_MAKE_VERSION(1, 2),	/* RS1 */
> +	PCI_PROTOCOL_VERSION_1_3 = PCI_MAKE_VERSION(1, 3),	/* VB */
>  };

What is "VB" ? Can we use a more meaningful name here? :-)

> +struct pci_function_description2 {
> +	u16	v_id;	/* vendor ID */
> +	u16	d_id;	/* device ID */
> +	u8	rev;
> +	u8	prog_intf;
> +	u8	subclass;
> +	u8	base_class;
> +	u32	subsystem_id;
> +	union win_slot_encoding win_slot;

space -> TAB?

> +/*
> + * Set NUMA node for the devices on the bus
> + */
> +static void pci_assign_numa_node(struct hv_pcibus_device *hbus)

IMO we'd better add a "hv_" prefix to this function's name, otherwise it looks
more like a generic PCI subsystem API.

> +{
> +	struct pci_dev *dev;
> +	struct pci_bus *bus = hbus->pci_bus;
> +	struct hv_pci_dev *hv_dev;
> +
> +	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		hv_dev = 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);
> +	}
> +}

Can you please give a brief background introduction to dev->numa_node,
e.g. how is it used here? -- is it used when a PCI device driver (e.g. the mlx
driver) asks the kernel to allocate memory for DMA, or allocate MSI interrupts?
How big is the performance gain in the tests? I'm curious as it looks unclear
to me how dev->numa_node is used by the PCI subsystem.

Thanks,
-- Dexuan