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From: Jiang Liu <liuj97@gmail.com>
To: Don Dutile <ddutile@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Yinghai Lu <yinghai@kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
	Taku Izumi <izumi.taku@jp.fujitsu.com>,
	"Rafael J . Wysocki" <rjw@sisk.pl>,
	Yijing Wang <wangyijing@huawei.com>,
	Xinwei Hu <huxinwei@huawei.com>,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [RFC PATCH v1 00/22] introduce PCI bus lock to serialize PCI hotplug operations
Date: Wed, 08 Aug 2012 23:49:54 +0800	[thread overview]
Message-ID: <50228AA2.1090004@gmail.com> (raw)
In-Reply-To: <50215A5B.2020508@redhat.com>

On 08/08/2012 02:11 AM, Don Dutile wrote:
> On 08/07/2012 12:10 PM, Jiang Liu wrote:
>> From: Jiang Liu<liuj97@gmail.com>
>>
>> This is the second take to resolve race conditions when hot-plugging PCI
>> devices/host bridges. Instead of using a globla lock to serialize all hotplug
>> operations as in previous version, now we introduce a state machine and bit
>> lock mechanism for PCI buses to serialize hotplug operations. For discussions
>> related to previous version, please refer to:
>> http://comments.gmane.org/gmane.linux.kernel.pci/15007
>>
>> This patch-set is still in early stages, so sending it out just requesting
>> for comments. Any comments are welcomed, especially about whether it's the
>> right/suitable way to solve these race condition issues.
>>
>> patch 1-5:
>>     Preparing for coming PCI bus lock
>> patch 6-7:
>>     Core of the new PCI bus lock mechanism.
>> patch 8-13:
>>     Enhance PCI core to support PCI bus lock mechanism.
>> patch 14-18:
>>     Enhance several PCI hotplug drivers to use PCI bus lock to serialize
>>     hotplug operations.
>> patch 19-20:
>>     Enable PCI bus lock mechanism for x86 and IA64, still need to enable
>>     PCI bus lock for other archs.
>> patch 21-22:
>>     Cleanups for unsed code.
>>
>> There are multiple methods to trigger PCI hotplug requests/operations
>> concurrently, such as:
>> 1. Sysfs interfaces exported by the PCI core subsystem
>>     /sys/devices/pcissss:bb/ssss:bb:dd.f/.../remove
>>     /sys/devices/pcissss:bb/ssss:bb:dd.f/.../rescan
>>     /sys/devices/pcissss:bb/ssss:bb:dd.f/.../pci_bus/ssss:bb/rescan
>>     /sys/bus/pci/rescan
>> 2. Sysfs interfaces exported by the PCI hotplug subsystem
>>     /sys/bus/pci/slots/xx/power
>> 3. PCI hotplug events triggered by PCI Hotplug Controllers
>> 4. ACPI hotplug events for PCI host bridges
>> 5. Driver binding/unbinding events
>>     binding/unbinding pci drivers with SR-IOV support
>>
> 6. PCI reset
>    --> a PCIe device-level reset is done by KVM when it assigns a device
>        to a guest.  a PCI config-save before reset, and PCI config-restore after reset
>        is done in this case.
>    --> VF devices are interesting, since they are reset, then bound to
>        pci-stub driver.  when more than 1 VF is enabled in a PF,
>        and several device-assignments are done simultaneously, you
>        get a storm of reset (save/restore pci cfg space), and pci-stub binding
>        (pci cfg read for resource allocation/deallocation), and depending on
>        the hw design: an AER caused by the FLR reset -- not suppose to, but
>        hw has bugs too! ;-)
>    PCI locking is 'challenged' in the above scenario.
> 
>   So, I ask: have you tried your patch set doing something like:
>     a) modprobe an SRIOV device with > 1 vf enabled
>   you may also have to do:
>     b) while assigning another SRIOV device's VF to another KVM guest
> 
> Unfortunately, the PCI cfg-space locking, esp. on x86 (ok, I'll say it:
> damn, mutually exclusive, IO-port-based cfg registers), doesn't lend itself
> to this multi-task, dynamic PCI scenario.
> Much less complicated on linearly-mapped, PCI-mmconf-only accesses.
> 
> - Don
Hi Don,
	Thanks for your comments. Haven't done such tests for SR-IOV yet. We will
try to find some NICs with SR-IOV capability for testing and will send the result
to you once done.
	Regards!
	Gerry


      reply	other threads:[~2012-08-08 15:50 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-07 16:10 [RFC PATCH v1 00/22] introduce PCI bus lock to serialize PCI hotplug operations Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 01/22] PCI: use pci_get_domain_bus_and_slot() to avoid race conditions Jiang Liu
2012-09-11 22:00   ` Bjorn Helgaas
2012-09-12  8:37     ` Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 02/22] PCI: trivial cleanups for drivers/pci/remove.c Jiang Liu
2012-09-11 22:03   ` Bjorn Helgaas
2012-09-12  8:50     ` Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 03/22] PCI: change PCI device management code to better follow device model Jiang Liu
2012-09-11 22:03   ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 04/22] PCI: split PCI bus device registration into two stages Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 05/22] PCI: introduce pci_bus_{get|put}() to manage PCI bus reference count Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 06/22] PCI: use a global lock to serialize PCI root bridge hotplug operations Jiang Liu
2012-09-11 22:57   ` Bjorn Helgaas
2012-09-12 15:42     ` Jiang Liu
2012-09-12 16:51       ` Bjorn Helgaas
2012-09-13 16:00         ` [PATCH 1/2] PCI: introduce root bridge hotplug safe interfaces to walk root buses Jiang Liu
2012-09-13 17:40           ` Bjorn Helgaas
2012-09-17 15:55             ` Jiang Liu
2012-09-17 16:24               ` Bjorn Helgaas
2012-09-18 21:39                 ` Bjorn Helgaas
2012-09-21 16:07                   ` [PATCH v4] PCI: introduce two interfaces to walk PCI buses Jiang Liu
2012-09-26 20:14                     ` Bjorn Helgaas
2012-09-13 16:00         ` [PATCH 2/2] PCI: remove host bridge hotplug unsafe interface pci_get_next_bus() Jiang Liu
2012-09-17 15:51         ` [RFC PATCH v1 06/22] PCI: use a global lock to serialize PCI root bridge hotplug operations Jiang Liu
2012-09-20 18:49         ` Paul E. McKenney
2012-08-07 16:10 ` [RFC PATCH v1 07/22] PCI: introduce PCI bus lock to serialize PCI " Jiang Liu
2012-09-11 23:24   ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 08/22] PCI: introduce hotplug safe search interfaces for PCI bus/device Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 09/22] PCI: enhance PCI probe logic to support PCI bus lock mechanism Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 10/22] PCI: enhance PCI bus specific " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 11/22] PCI: enhance PCI resource assignment " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 12/22] PCI: enhance PCI remove " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 13/22] PCI: make each PCI device hold a reference to its parent PCI bus Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 14/22] PCI/sysfs: use PCI bus lock to avoid race conditions Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 15/22] PCI/eeepc: " Jiang Liu
2012-09-11 23:18   ` Bjorn Helgaas
2012-09-12 14:24     ` [PATCH] eeepc-laptop: fix device reference count leakage in eeepc_rfkill_hotplug() Jiang Liu
2012-09-12 19:59       ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 16/22] PCI/asus-wmi: use PCI bus lock to avoid race conditions Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 17/22] PCI/pciehp: " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 18/22] PCI/acpiphp: " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 19/22] PCI/x86: enable PCI bus lock mechanism for x86 platforms Jiang Liu
2012-09-11 23:22   ` Bjorn Helgaas
2012-09-12  9:56     ` Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 20/22] PCI/IA64: enable PCI bus lock mechanism for IA64 platforms Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 21/22] PCI: cleanups for PCI bus lock implementation Jiang Liu
2012-09-11 23:21   ` Bjorn Helgaas
2012-09-12  8:58     ` Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 22/22] PCI: unexport pci_root_buses Jiang Liu
2012-08-07 18:11 ` [RFC PATCH v1 00/22] introduce PCI bus lock to serialize PCI hotplug operations Don Dutile
2012-08-08 15:49   ` Jiang Liu [this message]

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