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Commit 690f4304 authored by Jan Kiszka's avatar Jan Kiszka Committed by Thomas Gleixner
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PCI: Scan all functions when running over Jailhouse 



Per PCIe r4.0, sec 7.5.1.1.9, multi-function devices are required to have a
function 0.  Therefore, Linux scans for devices at function 0 (devfn
0/8/16/...) and only scans for other functions if function 0 has its
Multi-Function Device bit set or ARI or SR-IOV indicate there are more
functions.

The Jailhouse hypervisor may pass individual functions of a multi-function
device to a guest without passing function 0, which means a Linux guest
won't find them.

Change Linux PCI probing so it scans all function numbers when running as a
guest over Jailhouse.

This is technically prohibited by the spec, so it is possible that PCI
devices without the Multi-Function Device bit set may have unexpected
behavior in response to this probe.

Originally-by: default avatarBenedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: jailhouse-dev@googlegroups.com
Cc: Benedikt Spranger <b.spranger@linutronix.de>
Cc: linux-pci@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Link: https://lkml.kernel.org/r/06e279b2a3e06cf6689ab3975f8ab592bba02362.1520408357.git.jan.kiszka@siemens.com
parent 63338a38

arch/x86/pci/legacy.c

+3 −1
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
#include <linux/init.h>

#include <linux/export.h>

#include <linux/pci.h>

#include <asm/jailhouse_para.h>

#include <asm/pci_x86.h>



/*
@@ -34,13 +35,14 @@ int __init pci_legacy_init(void) 


void pcibios_scan_specific_bus(int busn)

{

	int stride = jailhouse_paravirt() ? 1 : 8;

	int devfn;

	u32 l;



	if (pci_find_bus(0, busn))

		return;



	for (devfn = 0; devfn < 256; devfn += 8) {

	for (devfn = 0; devfn < 256; devfn += stride) {

		if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&

		    l != 0x0000 && l != 0xffff) {

			DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);

drivers/pci/probe.c

+19 −3
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/pci-aspm.h>

#include <linux/aer.h>

#include <linux/acpi.h>

#include <linux/hypervisor.h>

#include <linux/irqdomain.h>

#include <linux/pm_runtime.h>

#include "pci.h"
@@ -2518,14 +2519,29 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus, 
{

	unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0;

	unsigned int start = bus->busn_res.start;

	unsigned int devfn, cmax, max = start;

	unsigned int devfn, fn, cmax, max = start;

	struct pci_dev *dev;

	int nr_devs;



	dev_dbg(&bus->dev, "scanning bus\n");



	/* Go find them, Rover! */

	for (devfn = 0; devfn < 0x100; devfn += 8)

		pci_scan_slot(bus, devfn);

	for (devfn = 0; devfn < 256; devfn += 8) {

		nr_devs = pci_scan_slot(bus, devfn);



		/*

		 * The Jailhouse hypervisor may pass individual functions of a

		 * multi-function device to a guest without passing function 0.

		 * Look for them as well.

		 */

		if (jailhouse_paravirt() && nr_devs == 0) {

			for (fn = 1; fn < 8; fn++) {

				dev = pci_scan_single_device(bus, devfn + fn);

				if (dev)

					dev->multifunction = 1;

			}

		}

	}



	/* Reserve buses for SR-IOV capability */

	used_buses = pci_iov_bus_range(bus);