Hotplug CallTrace: int acpiphp_enable_slot(struct acpiphp_slot *slot) _enable_device(slot); _pci_bus_add_devices(bus); # un-added new devs(all funcs in slot) will be added list_for_each_entry(dev, &bus->devices, bus_list) { if (dev->is_added) continue; pci_bus_add_device(dev); device_add(&dev->dev); dev->is_added = 1;
'dev->is_added' is used to trace if pci dev is added to bus, all funcs in same slot would be added to bus in enable_device(slot). So we need to clean all funcs of same slot in disable_device(slot).
But hot-remove exists bug: https://bugzilla.kernel.org/show_bug.cgi?id=43219 (dmesg and DSDT were attached in bz), detail:
. Boot up a Linux VM with 8 pci block devices which are the 8 functions in one pci slot. | # qemu-kvm ... | -drive file=images/u0,if=none,id=drv0,format=qcow2,cache=none \ | -device virtio-blk-pci,drive=drv0,id=v0,multifunction=on,addr=0x03.0 \ | .... | -drive file=images/u7,if=none,id=drv7,format=qcow2,cache=none \ | -device virtio-blk-pci,drive=drv7,id=v7,multifunction=on,addr=0x03.7 \
. Check devices in guest. | vm)# ls /dev/vd* | vda vdb vdc vde vdf vdg vdh | vm)# lspci |grep block | 00:03.0 SCSI storage controller: Red Hat, Inc Virtio block device | ... | 00:03.7 SCSI storage controller: Red Hat, Inc Virtio block device |
. Func1~7 still exist in guest after hot-removing the whole slot by qemu monitor cmd. | vm)# lspci |grep block (00:03.0 disappeared) | 00:03.1 SCSI storage controller: Red Hat, Inc Virtio block device (rev ff) | ... | 00:03.7 SCSI storage controller: Red Hat, Inc Virtio block device (rev ff) | vm)# ls /dev/vd* (vda disappeared) | vdb vdc vde vdf vdg vdh | vm)# mkfs /dev/vdb | INFO: task mkfs.ext2:1784 blocked for more than 120 seconds.
We process pci slot as a whole device in pciphp spec, seabios only defines one device for a slot in ACPI DSDT table. In acpiphp_glue.c:register_slot(), only one entry is added (for func#0) into 'slot->funcs' list. When we release the whole slot, only the entry in 'slot->funcs' will be cleaned, so func#1~7 could not be cleaned from system.
| drivers/pci/hotplug/acpiphp_glue.c: | static int disable_device(struct acpiphp_slot *slot) { | list_for_each_entry(func, &slot->funcs, sibling) { | pdev = pci_get_slot(slot->bridge->pci_bus, | PCI_DEVFN(slot->device, func->function)); | ..clean code.. // those code is only executed 1 time(for func#0) | __pci_remove_bus_device(pdev); | pci_dev_put(pdev);
Hotpluging multifunc of guests(WinXp/Win7) is fine.
--- v1 thread: http://marc.info/?t=131597601700003&r=1&w=2
Changes from v1: - rebase patch to latest linux.git - remove unnecessary multiplefunction check - rename 'i' to meaningful 'fn' - fix coding style
Changes from v2: - update detail reason(calltrace) to commitlog - remove hardcode 8, find funcs in pci devlist
Signed-off-by: Amos Kong akong@redhat.com --- drivers/pci/hotplug/acpiphp_glue.c | 9 +++++---- 1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func; - struct pci_dev *pdev; + struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check @@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
- pdev = pci_get_slot(slot->bridge->pci_bus, - PCI_DEVFN(slot->device, func->function)); - if (pdev) { + list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) { + if (PCI_SLOT(pdev->devfn) != slot->device) + continue; + pci_stop_bus_device(pdev); if (pdev->subordinate) { disable_bridges(pdev->subordinate);
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check
@@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
pdev = pci_get_slot(slot->bridge->pci_bus,PCI_DEVFN(slot->device, func->function));if (pdev) {
list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {if (PCI_SLOT(pdev->devfn) != slot->device)continue;
The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
BTW, what's the relationship with "[PATCH v3] hotplug: add device per func in ACPI DSDT tables"? Seems they are both solving the same issue.
pci_stop_bus_device(pdev); if (pdev->subordinate) { disable_bridges(pdev->subordinate);-- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check
@@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
pdev = pci_get_slot(slot->bridge->pci_bus,PCI_DEVFN(slot->device, func->function));if (pdev) {
list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {if (PCI_SLOT(pdev->devfn) != slot->device)continue;The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
BTW, what's the relationship with "[PATCH v3] hotplug: add device per func in ACPI DSDT tables"? Seems they are both solving the same issue.
That's a bios patch. It's needed if you want broken linux to work. This makes linux behave properly on the original bios.
pci_stop_bus_device(pdev); if (pdev->subordinate) { disable_bridges(pdev->subordinate);-- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/11/2012 02:55 AM, Michael S. Tsirkin wrote:
On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check
@@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
pdev = pci_get_slot(slot->bridge->pci_bus,PCI_DEVFN(slot->device, func->function));if (pdev) {
list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {if (PCI_SLOT(pdev->devfn) != slot->device)continue;The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
BTW, what's the relationship with "[PATCH v3] hotplug: add device per func in ACPI DSDT tables"? Seems they are both solving the same issue.
Two work need to be done when we disable a slot, cleaning configuration(in OS) and power off slot.
Currently the second part(power off) works fine, all funcs disappear from "(qemu)#info block" after hot-remove slot. The only problem is func 1~7 are not unconfigured, so I NAKed seabios patch, and try to fix this problem in pci driver.
(btw, winxp & win7 hotplug works currently)
/** * acpiphp_disable_slot - power off slot * @slot: ACPI PHP slot */ int acpiphp_disable_slot(struct acpiphp_slot *slot) { mutex_lock(&slot->crit_sect);
/* unconfigure all functions */ retval = disable_device(slot);
/* power off all functions */ retval = power_off_slot(slot); .... }
That's a bios patch. It's needed if you want broken linux to work. This makes linux behave properly on the original bios.
pci_stop_bus_device(pdev); if (pdev->subordinate) { disable_bridges(pdev->subordinate);
On 05/11/2012 07:54 AM, Amos Kong wrote:
On 05/11/2012 02:55 AM, Michael S. Tsirkin wrote:
On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check
@@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
pdev = pci_get_slot(slot->bridge->pci_bus,PCI_DEVFN(slot->device, func->function));if (pdev) {
list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {if (PCI_SLOT(pdev->devfn) != slot->device)continue;The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
pci_bus_sem lock is only request for writing &bus->devices list, right ? and this protection already exists in pci_destory_dev().
static int disable_device(struct acpiphp_slot *slot) _ list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) { _ __pci_remove_bus_device(pdev); _ pci_destroy_dev(dev);
static void pci_destroy_dev(struct pci_dev *dev) { /* Remove the device from the device lists, and prevent any further * list accesses from this device */ down_write(&pci_bus_sem); list_del(&dev->bus_list); dev->bus_list.next = dev->bus_list.prev = NULL; up_write(&pci_bus_sem); ... }
On 05/11/2012 08:24 AM, Amos Kong wrote:
On 05/11/2012 07:54 AM, Amos Kong wrote:
On 05/11/2012 02:55 AM, Michael S. Tsirkin wrote:
On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
struct pci_dev *pdev, *tmp; struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check
@@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
pdev = pci_get_slot(slot->bridge->pci_bus,PCI_DEVFN(slot->device, func->function));if (pdev) {
list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {if (PCI_SLOT(pdev->devfn) != slot->device)continue;The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
pci_bus_sem lock is only request for writing &bus->devices list, right ? and this protection already exists in pci_destory_dev().
That's for writer. For reader to walk the pci_bus->devices list, you also need to acquire the reader lock by down_read(&pci_bus_sem). Please refer to pci_get_slot() for example. This especially import for native OS because there may be multiple PCI slots/devices on the bus.
On Fri, May 11, 2012 at 8:00 AM, Jiang Liu liuj97@gmail.com wrote:
On 05/11/2012 08:24 AM, Amos Kong wrote:
On 05/11/2012 07:54 AM, Amos Kong wrote:
On 05/11/2012 02:55 AM, Michael S. Tsirkin wrote:
On Fri, May 11, 2012 at 01:09:13AM +0800, Jiang Liu wrote:
On 05/10/2012 11:44 PM, Amos Kong wrote:
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c index 806c44f..a7442d9 100644 --- a/drivers/pci/hotplug/acpiphp_glue.c +++ b/drivers/pci/hotplug/acpiphp_glue.c @@ -885,7 +885,7 @@ static void disable_bridges(struct pci_bus *bus) static int disable_device(struct acpiphp_slot *slot) { struct acpiphp_func *func;
- struct pci_dev *pdev;
- struct pci_dev *pdev, *tmp;
struct pci_bus *bus = slot->bridge->pci_bus;
/* The slot will be enabled when func 0 is added, so check @@ -902,9 +902,10 @@ static int disable_device(struct acpiphp_slot *slot) func->bridge = NULL; }
- pdev = pci_get_slot(slot->bridge->pci_bus,
- PCI_DEVFN(slot->device, func->function));
- if (pdev) {
- list_for_each_entry_safe(pdev, tmp, &bus->devices, bus_list) {
- if (PCI_SLOT(pdev->devfn) != slot->device)
- continue;
I think the concept is good: in enable_device(), we use pci_scan_slot(), which scans all possible functions in the slot. So in disable_device() we should do something symmetric to remove all the functions.
The pci_bus_sem lock should be acquired when walking the bus->devices list. Otherwise it may cause invalid memory access if another thread is modifying the bus->devices list concurrently.
pci_bus_sem lock is only request for writing &bus->devices list, right ? and this protection already exists in pci_destory_dev().
That's for writer. For reader to walk the pci_bus->devices list, you also need to acquire the reader lock by down_read(&pci_bus_sem). Please refer to pci_get_slot() for example. This especially import for native OS because there may be multiple PCI slots/devices on the bus.
There is a lot of existing code that walks bus->devices without holding pci_bus_sem, but most of it is boot-time code that is arguably safe (though I think things like pcibios_fixup_bus() are poorly designed and don't fit well in the hotplug-enabled world).
In this case, I do think we need to protect against updates while we're walking bus->devices. It's probably not trivial because __pci_remove_bus_device() calls pci_destroy_dev(), where we do the down_write(), so simply wrapping the whole thing with down_read() will cause a deadlock.
Kenji-san, Yinghai, do you have any input?
Bjorn
-
Amos Kong -
Bjorn Helgaas -
Jiang Liu -
Michael S. Tsirkin