From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wu, Feng" Subject: Requesting for freeze exception for VT-d posted-interrupts Date: Mon, 13 Jul 2015 06:55:30 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Language: en-US List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "wei.liu2@citrix.com" , "xen-devel@lists.xen.org" Cc: "Tian, Kevin" , "Wu, Feng" , George Dunlap , "andrew.cooper3@citrix.com" , "Wang, Yong Y" , "Jan Beulich (JBeulich@suse.com)" , "Zhang, Yang Z" List-Id: xen-devel@lists.xenproject.org Hi maintainers, We would like to request an extension for freeze exception for VT-d posted-interrupts patch-set. 1. clarify the state of patch series / feature. [v3 01/15] Vt-d Posted-interrupt (PI) design Reviewed-by: Kevin Tian [v3 02/15] Add helper macro for X86_FEATURE_CX16 feature detection Reviewed-by: Kevin Tian Reviewed-by: Andrew Cooper [v3 04/15] iommu: Add iommu_intpost to control VT-d Posted-Interrupts feature Reviewed-by: Kevin Tian [v3 06/15] vmx: Extend struct pi_desc to support VT-d Posted-Interrupts Reviewed-by: Andrew Cooper Acked-by: Kevin Tian [v3 07/15] vmx: Initialize VT-d Posted-Interrupts Descriptor Acked-by: Kevin Tian [v3 09/15] vt-d: Extend struct iremap_entry to support VT-d Posted-Interrupts Acked-by: Kevin Tian [v3 10/15] vt-d: Add API to update IRTE when VT-d PI is used Acked-by: Kevin Tian [v3 13/15] vmx: Properly handle notification event when vCPU is running Acked-by: Kevin Tian [v3 14/15] Update Posted-Interrupts Descriptor during vCPU scheduling Acked-by: Kevin Tian [v3 15/15] Add a command line parameter for VT-d posted-interrupts Reviewed-by: Kevin Tian 2. explain why it needs to be in this release (benefits). VT-d posted-interrupts is an important interrupt virtualization feature for device pass-through, the running guest can handle external interrupts in non-root mode, hence it can eliminate the VM-Exits caused by external interrupts. Please refer to the design doc: http://lists.xenproject.org/archives/html/xen-devel/2015-06/msg03691.html >>From our experimental environment, after using VT-d posted-interrupts, we measured 25% improvement in transaction rate netperf TCP_RR benchmark and 28% reduction in host CPU utilization when using assigned devices. (10G NIC in my test). 3. explain why it doesn't break things (risks). This feature only exists in Broadwell Server platform, it has no effect on the current hardware. 4. CC relevant maintainers and release manager. Done There are two main outstanding issues so far: 1. Jan's security concern. I have proposed some solutions but Jan still has some problems with my proposals. It would be great if Jan can give a clear proposal so that we can discuss and keep making progress. 2. Scheduler issue: there are conflicts among maintainers Jan/George/Dario. I would agree with Jan's suggestion below: " Doing this in a central place is certainly the right approach, but adding an arch hook that needs to be called everywhere vcpu_runstate_change() wouldn't serve that purpose. Instead we'd need to replace all current vcpu_runstate_change() calls with calls to a new function calling both this and the to be added arch hook." However, if different maintainers still hold different opinions, I would appreciate it if maintainers can reach consensus among themselves so that we can keep making progress Thanks, Feng