korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-28 22:54:05 +08:00
Code Issues Packages Projects Releases Wiki Activity

platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe

Browse Source 
p2sb_bar() unhides P2SB device to get resources from the device. It
guards the operation by locking pci_rescan_remove_lock so that parallel
rescans do not find the P2SB device. However, this lock causes deadlock
when PCI bus rescan is triggered by /sys/bus/pci/rescan. The rescan
locks pci_rescan_remove_lock and probes PCI devices. When PCI devices
call p2sb_bar() during probe, it locks pci_rescan_remove_lock again.
Hence the deadlock.

To avoid the deadlock, do not lock pci_rescan_remove_lock in p2sb_bar().
Instead, do the lock at fs_initcall. Introduce p2sb_cache_resources()
for fs_initcall which gets and caches the P2SB resources. At p2sb_bar(),
refer the cache and return to the caller.

Before operating the device at P2SB DEVFN for resource cache, check
that its device class is PCI_CLASS_MEMORY_OTHER 0x0580 that PCH
specifications define. This avoids unexpected operation to other devices
at the same DEVFN.

Link: https://lore.kernel.org/linux-pci/6xb24fjmptxxn5js2fjrrddjae6twex5bjaftwqsuawuqqqydx@7cl3uik5ef6j/
Fixes: 9745fb0747 ("platform/x86/intel: Add Primary to Sideband (P2SB) bridge support")
Cc: stable@vger.kernel.org
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20240108062059.3583028-2-shinichiro.kawasaki@wdc.com
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Tested-by Klara Modin <klarasmodin@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
This commit is contained in:
Shin'ichiro Kawasaki 2024-01-08 15:20:58 +09:00 committed by Hans de Goede
parent 416de0246f
commit 5913320eb0
1 changed files with 150 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

202
drivers/platform/x86/p2sb.c
View File

@ -26,6 +26,21 @@ static const struct x86_cpu_id p2sb_cpu_ids[] = {
{}
};
/*
* Cache BAR0 of P2SB device functions 0 to 7.
* TODO: The constant 8 is the number of functions that PCI specification
* defines. Same definitions exist tree-wide. Unify this definition and
* the other definitions then move to include/uapi/linux/pci.h.
*/
#define NR_P2SB_RES_CACHE 8
struct p2sb_res_cache {
u32 bus_dev_id;
struct resource res;
};
static struct p2sb_res_cache p2sb_resources[NR_P2SB_RES_CACHE];
static int p2sb_get_devfn(unsigned int *devfn)
{
unsigned int fn = P2SB_DEVFN_DEFAULT;
@ -39,8 +54,16 @@ static int p2sb_get_devfn(unsigned int *devfn)
return 0;
}
static bool p2sb_valid_resource(struct resource *res)
{
if (res->flags)
return true;
return false;
}
/* Copy resource from the first BAR of the device in question */
static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
static void p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
{
struct resource *bar0 = &pdev->resource[0];
@ -56,22 +79,108 @@ static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
mem->end = bar0->end;
mem->flags = bar0->flags;
mem->desc = bar0->desc;
}
static void p2sb_scan_and_cache_devfn(struct pci_bus *bus, unsigned int devfn)
{
struct p2sb_res_cache *cache = &p2sb_resources[PCI_FUNC(devfn)];
struct pci_dev *pdev;
pdev = pci_scan_single_device(bus, devfn);
if (!pdev)
return;
p2sb_read_bar0(pdev, &cache->res);
cache->bus_dev_id = bus->dev.id;
pci_stop_and_remove_bus_device(pdev);
}
static int p2sb_scan_and_cache(struct pci_bus *bus, unsigned int devfn)
{
unsigned int slot, fn;
if (PCI_FUNC(devfn) == 0) {
/*
* When function number of the P2SB device is zero, scan it and
* other function numbers, and if devices are available, cache
* their BAR0s.
*/
slot = PCI_SLOT(devfn);
for (fn = 0; fn < NR_P2SB_RES_CACHE; fn++)
p2sb_scan_and_cache_devfn(bus, PCI_DEVFN(slot, fn));
} else {
/* Scan the P2SB device and cache its BAR0 */
p2sb_scan_and_cache_devfn(bus, devfn);
}
if (!p2sb_valid_resource(&p2sb_resources[PCI_FUNC(devfn)].res))
return -ENOENT;
return 0;
}
static int p2sb_scan_and_read(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
static struct pci_bus *p2sb_get_bus(struct pci_bus *bus)
{
struct pci_dev *pdev;
static struct pci_bus *p2sb_bus;
bus = bus ?: p2sb_bus;
if (bus)
return bus;
/* Assume P2SB is on the bus 0 in domain 0 */
p2sb_bus = pci_find_bus(0, 0);
return p2sb_bus;
}
static int p2sb_cache_resources(void)
{
unsigned int devfn_p2sb;
u32 value = P2SBC_HIDE;
struct pci_bus *bus;
u16 class;
int ret;
pdev = pci_scan_single_device(bus, devfn);
if (!pdev)
/* Get devfn for P2SB device itself */
ret = p2sb_get_devfn(&devfn_p2sb);
if (ret)
return ret;
bus = p2sb_get_bus(NULL);
if (!bus)
return -ENODEV;
ret = p2sb_read_bar0(pdev, mem);
/*
* When a device with same devfn exists and its device class is not
* PCI_CLASS_MEMORY_OTHER for P2SB, do not touch it.
*/
pci_bus_read_config_word(bus, devfn_p2sb, PCI_CLASS_DEVICE, &class);
if (!PCI_POSSIBLE_ERROR(class) && class != PCI_CLASS_MEMORY_OTHER)
return -ENODEV;
/*
* Prevent concurrent PCI bus scan from seeing the P2SB device and
* removing via sysfs while it is temporarily exposed.
*/
pci_lock_rescan_remove();
/*
* The BIOS prevents the P2SB device from being enumerated by the PCI
* subsystem, so we need to unhide and hide it back to lookup the BAR.
* Unhide the P2SB device here, if needed.
*/
pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0);
ret = p2sb_scan_and_cache(bus, devfn_p2sb);
/* Hide the P2SB device, if it was hidden */
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE);
pci_unlock_rescan_remove();
pci_stop_and_remove_bus_device(pdev);
return ret;
}
@ -81,64 +190,53 @@ static int p2sb_scan_and_read(struct pci_bus *bus, unsigned int devfn, struct re
* @devfn: PCI slot and function to communicate with
* @mem: memory resource to be filled in
*
* The BIOS prevents the P2SB device from being enumerated by the PCI
* subsystem, so we need to unhide and hide it back to lookup the BAR.
*
* if @bus is NULL, the bus 0 in domain 0 will be used.
* If @bus is NULL, the bus 0 in domain 0 will be used.
* If @devfn is 0, it will be replaced by devfn of the P2SB device.
*
* Caller must provide a valid pointer to @mem.
*
* Locking is handled by pci_rescan_remove_lock mutex.
*
* Return:
* 0 on success or appropriate errno value on error.
*/
int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
{
struct pci_dev *pdev_p2sb;
unsigned int devfn_p2sb;
u32 value = P2SBC_HIDE;
struct p2sb_res_cache *cache;
int ret;
/* Get devfn for P2SB device itself */
ret = p2sb_get_devfn(&devfn_p2sb);
if (ret)
return ret;
/* if @bus is NULL, use bus 0 in domain 0 */
bus = bus ?: pci_find_bus(0, 0);
/*
* Prevent concurrent PCI bus scan from seeing the P2SB device and
* removing via sysfs while it is temporarily exposed.
*/
pci_lock_rescan_remove();
/* Unhide the P2SB device, if needed */
pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0);
pdev_p2sb = pci_scan_single_device(bus, devfn_p2sb);
if (devfn)
ret = p2sb_scan_and_read(bus, devfn, mem);
else
ret = p2sb_read_bar0(pdev_p2sb, mem);
pci_stop_and_remove_bus_device(pdev_p2sb);
/* Hide the P2SB device, if it was hidden */
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE);
pci_unlock_rescan_remove();
if (ret)
return ret;
if (mem->flags == 0)
bus = p2sb_get_bus(bus);
if (!bus)
return -ENODEV;
if (!devfn) {
ret = p2sb_get_devfn(&devfn);
if (ret)
return ret;
}
cache = &p2sb_resources[PCI_FUNC(devfn)];
if (cache->bus_dev_id != bus->dev.id)
return -ENODEV;
if (!p2sb_valid_resource(&cache->res))
return -ENOENT;
memcpy(mem, &cache->res, sizeof(*mem));
return 0;
}
EXPORT_SYMBOL_GPL(p2sb_bar);
static int __init p2sb_fs_init(void)
{
p2sb_cache_resources();
return 0;
}
/*
* pci_rescan_remove_lock to avoid access to unhidden P2SB devices can
* not be locked in sysfs pci bus rescan path because of deadlock. To
* avoid the deadlock, access to P2SB devices with the lock at an early
* step in kernel initialization and cache required resources. This
* should happen after subsys_initcall which initializes PCI subsystem
* and before device_initcall which requires P2SB resources.
*/
fs_initcall(p2sb_fs_init);