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: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Bjorn 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

diff --git a/arch/x86/pci/legacy.c b/arch/x86/pci/legacy.c
index 1cb01abcb1bee88befdb2fbce8c989104cfa737f..dfbe6ac38830543be4979c9ff0b7dc6eb99346ec 100644 (file)
--- a/arch/x86/pci/legacy.c
+++ b/arch/x86/pci/legacy.c
@@ -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);

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ef5377438a1e65df31790a61472e34e708a835ab..3c365dc996e71e103bf5891749d52bee1af01f26 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -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);