[PATCH 2/2] PCI: Replace pci_dev->broken_parity_status with accessors

[Maurice Hieronymus <mhi@xxxxxxxxxxx>]

`broken_parity_status` shares a C bitfield word in `struct pci_dev`
with many other bits. `broken_parity_status_store()` writes it from
sysfs at any time without taking any lock, so userspace can make it
race with every other writer of the same word, e.g. `pci_set_master()`
from a runtime PM resume path, and updates of neighboring bits can be
lost.

Move the bit into the `flags` bitmap modified with atomic bitops,
using the accessor pattern introduced by the previous commit.

Signed-off-by: Maurice Hieronymus <mhi@xxxxxxxxxxx>
---
 drivers/edac/edac_pci_sysfs.c | 4 ++--
 drivers/pci/pci-sysfs.c       | 4 ++--
 include/linux/pci.h           | 5 ++++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/edac_pci_sysfs.c b/drivers/edac/edac_pci_sysfs.c
index 9f437f648e4e..fadc61235f1f 100644
--- a/drivers/edac/edac_pci_sysfs.c
+++ b/drivers/edac/edac_pci_sysfs.c
@@ -554,7 +554,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
        /* check the status reg for errors on boards NOT marked as broken
         * if broken, we cannot trust any of the status bits
         */
-       if (status && !dev->broken_parity_status) {
+       if (status && !pci_dev_broken_parity_status(dev)) {
                if (status & (PCI_STATUS_SIG_SYSTEM_ERROR)) {
                        edac_printk(KERN_CRIT, EDAC_PCI,
                                "Signaled System Error on %s\n",
@@ -593,7 +593,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
                /* check the secondary status reg for errors,
                 * on NOT broken boards
                 */
-               if (status && !dev->broken_parity_status) {
+               if (status && !pci_dev_broken_parity_status(dev)) {
                        if (status & (PCI_STATUS_SIG_SYSTEM_ERROR)) {
                                edac_printk(KERN_CRIT, EDAC_PCI, "Bridge "
                                        "Signaled System Error on %s\n",
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5ec0b245a69b..5e094d1e23e3 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -80,7 +80,7 @@ static ssize_t broken_parity_status_show(struct device *dev,
                                         char *buf)
 {
        struct pci_dev *pdev = to_pci_dev(dev);
-       return sysfs_emit(buf, "%u\n", pdev->broken_parity_status);
+       return sysfs_emit(buf, "%u\n", pci_dev_broken_parity_status(pdev));
 }
 
 static ssize_t broken_parity_status_store(struct device *dev,
@@ -93,7 +93,7 @@ static ssize_t broken_parity_status_store(struct device *dev,
        if (kstrtoul(buf, 0, &val) < 0)
                return -EINVAL;
 
-       pdev->broken_parity_status = !!val;
+       pci_dev_assign_broken_parity_status(pdev, val);
 
        return count;
 }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9964646bdd46..fdcd9b1b7371 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -347,10 +347,13 @@ struct rcec_ea;
  *             bookkeeping state, maintained by pci_set_master(),
  *             pci_clear_master() and pci_disable_device(); modifying it
  *             does not itself change the hardware state.
+ * @PCI_DEV_FLAG_BROKEN_PARITY_STATUS: Device generates false positive
+ *             parity errors; set via sysfs.
  * @PCI_DEV_FLAG_COUNT: Number of defined struct_pci_dev_flags.
  */
 enum struct_pci_dev_flags {
        PCI_DEV_FLAG_BUSMASTER = 0,
+       PCI_DEV_FLAG_BROKEN_PARITY_STATUS = 1,
 
        PCI_DEV_FLAG_COUNT
 };
@@ -482,7 +485,6 @@ struct pci_dev {
 
        unsigned int    no_msi:1;               /* May not use MSI */
        unsigned int    block_cfg_access:1;     /* Config space access blocked 
*/
-       unsigned int    broken_parity_status:1; /* Generates false positive 
parity */
        unsigned int    irq_reroute_variant:2;  /* Needs IRQ rerouting variant 
*/
        unsigned int    msi_enabled:1;
        unsigned int    msix_enabled:1;
@@ -626,6 +628,7 @@ static inline void pci_dev_assign_##accessor_name(struct 
pci_dev *pdev, bool val
 }
 
 __create_pci_dev_flag_accessors(busmaster, PCI_DEV_FLAG_BUSMASTER);
+__create_pci_dev_flag_accessors(broken_parity_status, 
PCI_DEV_FLAG_BROKEN_PARITY_STATUS);
 
 #undef __create_pci_dev_flag_accessors
 

-- 
2.51.2