PCI: Fix is_added/is_busmaster race condition

When a PCI device is detected, pdev->is_added is set to 1 and proc and
sysfs entries are created.

When the device is removed, pdev->is_added is checked for one and then
device is detached with clearing of proc and sys entries and at end,
pdev->is_added is set to 0.

is_added and is_busmaster are bit fields in pci_dev structure sharing same
memory location.

A strange issue was observed with multiple removal and rescan of a PCIe
NVMe device using sysfs commands where is_added flag was observed as zero
instead of one while removing device and proc,sys entries are not cleared.
This causes issue in later device addition with warning message
"proc_dir_entry" already registered.

Debugging revealed a race condition between the PCI core setting the
is_added bit in pci_bus_add_device() and the NVMe driver reset work-queue
setting the is_busmaster bit in pci_set_master().  As these fields are not
handled atomically, that clears the is_added bit.

Move the is_added bit to a separate private flag variable and use atomic
functions to set and retrieve the device addition state.  This avoids the
race because is_added no longer shares a memory location with is_busmaster.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=200283
Signed-off-by: Hari Vyas <hari.vyas@broadcom.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Hari Vyas 2018-07-03 14:35:41 +05:30 committed by Bjorn Helgaas
parent a54e43f993
commit 44bda4b7d2
9 changed files with 27 additions and 12 deletions

View File

@ -42,6 +42,8 @@
#include <asm/ppc-pci.h>
#include <asm/eeh.h>
#include "../../../drivers/pci/pci.h"
/* hose_spinlock protects accesses to the the phb_bitmap. */
static DEFINE_SPINLOCK(hose_spinlock);
LIST_HEAD(hose_list);
@ -1014,7 +1016,7 @@ void pcibios_setup_bus_devices(struct pci_bus *bus)
/* Cardbus can call us to add new devices to a bus, so ignore
* those who are already fully discovered
*/
if (dev->is_added)
if (pci_dev_is_added(dev))
continue;
pcibios_setup_device(dev);

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@ -46,6 +46,7 @@
#include "powernv.h"
#include "pci.h"
#include "../../../../drivers/pci/pci.h"
#define PNV_IODA1_M64_NUM 16 /* Number of M64 BARs */
#define PNV_IODA1_M64_SEGS 8 /* Segments per M64 BAR */
@ -3138,7 +3139,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
struct pci_dn *pdn;
int mul, total_vfs;
if (!pdev->is_physfn || pdev->is_added)
if (!pdev->is_physfn || pci_dev_is_added(pdev))
return;
pdn = pci_get_pdn(pdev);

View File

@ -71,6 +71,7 @@
#include <asm/security_features.h>
#include "pseries.h"
#include "../../../../drivers/pci/pci.h"
int CMO_PrPSP = -1;
int CMO_SecPSP = -1;
@ -664,7 +665,7 @@ static void pseries_pci_fixup_iov_resources(struct pci_dev *pdev)
const int *indexes;
struct device_node *dn = pci_device_to_OF_node(pdev);
if (!pdev->is_physfn || pdev->is_added)
if (!pdev->is_physfn || pci_dev_is_added(pdev))
return;
/*Firmware must support open sriov otherwise dont configure*/
indexes = of_get_property(dn, "ibm,open-sriov-vf-bar-info", NULL);

View File

@ -330,7 +330,7 @@ void pci_bus_add_device(struct pci_dev *dev)
return;
}
dev->is_added = 1;
pci_dev_assign_added(dev, true);
}
EXPORT_SYMBOL_GPL(pci_bus_add_device);
@ -347,14 +347,14 @@ void pci_bus_add_devices(const struct pci_bus *bus)
list_for_each_entry(dev, &bus->devices, bus_list) {
/* Skip already-added devices */
if (dev->is_added)
if (pci_dev_is_added(dev))
continue;
pci_bus_add_device(dev);
}
list_for_each_entry(dev, &bus->devices, bus_list) {
/* Skip if device attach failed */
if (!dev->is_added)
if (!pci_dev_is_added(dev))
continue;
child = dev->subordinate;
if (child)

View File

@ -509,7 +509,7 @@ static void enable_slot(struct acpiphp_slot *slot)
list_for_each_entry(dev, &bus->devices, bus_list) {
/* Assume that newly added devices are powered on already. */
if (!dev->is_added)
if (!pci_dev_is_added(dev))
dev->current_state = PCI_D0;
}

View File

@ -288,6 +288,7 @@ struct pci_sriov {
/* pci_dev priv_flags */
#define PCI_DEV_DISCONNECTED 0
#define PCI_DEV_ADDED 1
static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
{
@ -300,6 +301,16 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev)
return test_bit(PCI_DEV_DISCONNECTED, &dev->priv_flags);
}
static inline void pci_dev_assign_added(struct pci_dev *dev, bool added)
{
assign_bit(PCI_DEV_ADDED, &dev->priv_flags, added);
}
static inline bool pci_dev_is_added(const struct pci_dev *dev)
{
return test_bit(PCI_DEV_ADDED, &dev->priv_flags);
}
#ifdef CONFIG_PCI_ATS
void pci_restore_ats_state(struct pci_dev *dev);
#else

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@ -2433,13 +2433,13 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
dev = pci_scan_single_device(bus, devfn);
if (!dev)
return 0;
if (!dev->is_added)
if (!pci_dev_is_added(dev))
nr++;
for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn)) {
dev = pci_scan_single_device(bus, devfn + fn);
if (dev) {
if (!dev->is_added)
if (!pci_dev_is_added(dev))
nr++;
dev->multifunction = 1;
}

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@ -19,11 +19,12 @@ static void pci_stop_dev(struct pci_dev *dev)
{
pci_pme_active(dev, false);
if (dev->is_added) {
if (pci_dev_is_added(dev)) {
device_release_driver(&dev->dev);
pci_proc_detach_device(dev);
pci_remove_sysfs_dev_files(dev);
dev->is_added = 0;
pci_dev_assign_added(dev, false);
}
if (dev->bus->self)

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@ -368,7 +368,6 @@ struct pci_dev {
unsigned int transparent:1; /* Subtractive decode bridge */
unsigned int multifunction:1; /* Multi-function device */
unsigned int is_added:1;
unsigned int is_busmaster:1; /* Is busmaster */
unsigned int no_msi:1; /* May not use MSI */
unsigned int no_64bit_msi:1; /* May only use 32-bit MSIs */