Difference between revisions of "Xen ARM TODO"

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== In progress ==
 
== In progress ==
 
== Known Bugs ==
 
=== General ===
 
 
==== Domain 0 memory limitation due to 1:1 mapping ====
 
 
The use of the 1:1 workaround for dom0's memory (needed on platforms without an I/O SMMU, which is currently all) limits the maximum size of dom0. By carefully positioning the Xen and initial kernel/initrd/dtb binaries at the top of RAM dom0 is able to make use of up to 1/2 of the host RAM. The remainder is available for guest use. In general dom0 should be made quite small anyway. For more information see:
 
* http://lists.xen.org/archives/html/xen-devel/2013-12/msg02239.html
 
* http://lists.xen.org/archives/html/xen-devel/2014-01/msg00885.html
 
 
This should be addressed in a future release by supporting multiple memory banks for dom0.
 
 
=== Versatile Express ===
 
 
=== Arndale Board ===
 
   
 
== Open Work Items ==
 
== Open Work Items ==
 
{{Open Project
 
|Project=vGIC interrupt prioritisation
 
|Desc=
 
Currently the vGIC only implements a very basic form of interrupt priority, in particular it is not able to preempt an inflight lower priority interrupt when a new higher priority one occurs. The emulation needs to consider the vCPUs current IAR as well as the priorities of pending and inflight interrupts.
 
}}
 
 
{{Open Project
 
|Project=VCPU virtual time support
 
|Desc=Currently the concept of virtual time exposed to the guests is very simplistic and is just a static offset from physical time based on the time when the guest was started. We need to consider if this is actually what is needed/wanted and consider cases such as stolen time etc.
 
}}
 
 
{{Open Project
 
|Project=IOMMU support in Xen
 
|Desc=
 
write a driver in Xen for the ARM System Memory Management Unit (SMMU), use it to assign devices to Dom0.
 
}}
 
   
 
{{Open Project
 
{{Open Project
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|Desc=
 
|Desc=
 
Make VM save/restore and VM migration work on ARM.
 
Make VM save/restore and VM migration work on ARM.
|References=InProgress: http://lists.xen.org/archives/html/xen-devel/2013-10/msg00192.html
+
|References=An initial prototype was written a couple of years ago for arm32 but never completed: http://lists.xen.org/archives/html/xen-devel/2014-06/msg02076.html
}}
 
{{Open Project
 
|Project=Use Superpage mappings for P2M
 
|Desc=
 
Currently we use 4K pages everywhere. Xen should attempt to use 2MB mappings in the P2M wherever possible.
 
This will have significant performance benefits.
 
Need to do 2MB ballooning too.
 
 
}}
 
}}
  +
 
{{Open Project
 
{{Open Project
|Project=Device assignment to DomUs
+
|Project=PCI device assignment to DomUs
 
|Desc=
 
|Desc=
 
Assign one or more devices to an unprivileged guest, re-program the SMMU accordingly.
 
Assign one or more devices to an unprivileged guest, re-program the SMMU accordingly.
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{{Open Project
 
{{Open Project
|Project=Expose Wallclock time to guests
+
|Project=ITS support
  +
|Desc=
|Desc=Current Xen on ARM does not popular the wallclock time fields of the shared info with anything useful. It should do so...
 
  +
Physical and virtual ITS support for GICv3.
}}
 
  +
|References=Work underway: http://marc.info/?i=1426775889-29442-1-git-send-email-vijay.kilari%40gmail.com
 
{{Open Project
 
|Project=Support GIC v3
 
|Desc=New hardware will come with GIC v3. Currently Xen only support GIC v2
 
 
}}
 
}}
   
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|References=http://lists.xen.org/archives/html/xen-devel/2014-02/msg01880.html
 
|References=http://lists.xen.org/archives/html/xen-devel/2014-02/msg01880.html
 
}}
 
}}
  +
  +
{{Open Project
  +
|Project=Investigation on HCR.FB
  +
|Desc=Setting HCR.FB will upgrade local flush instructions (TLB, instruction cache, branch predictor) to innershareable. It would be nice to benchmark the performance impact on a UP-aware kernel and see if this could be reduced by flushing when a vCPU is migrating to another physical CPUs.
  +
|References=http://lists.xen.org/archives/html/xen-devel/2016-04/msg03157.html
  +
}}
  +
  +
[[Category:XenARM]]

Latest revision as of 10:22, 27 April 2016

This is a list of open work items and known bugs for the Xen on ARM with virtualization extension project.


In progress

Open Work Items

Save/restore and migration
Contact: xen-devel@lists.xen.org
Description: Make VM save/restore and VM migration work on ARM.
References: An initial prototype was written a couple of years ago for arm32 but never completed: http://lists.xen.org/archives/html/xen-devel/2014-06/msg02076.html

PCI device assignment to DomUs
Contact: xen-devel@lists.xen.org
Description: Assign one or more devices to an unprivileged guest, re-program the SMMU accordingly.
References: Not specified, useful references.

ITS support
Contact: xen-devel@lists.xen.org
Description: Physical and virtual ITS support for GICv3.
References: Work underway: http://marc.info/?i=1426775889-29442-1-git-send-email-vijay.kilari%40gmail.com

More flexible early printk support
Contact: xen-devel@lists.xen.org
Description: Allow a single Xen binary to support multiple platforms for early_printk Rather than parsing the DTB early in asm to get the command line it would probably be sufficient to have a magic hex byte at a specific offset which could be edited by a simple tool.
References: http://lists.xen.org/archives/html/xen-devel/2014-02/msg01880.html

Investigation on HCR.FB
Contact: xen-devel@lists.xen.org
Description: Setting HCR.FB will upgrade local flush instructions (TLB, instruction cache, branch predictor) to innershareable. It would be nice to benchmark the performance impact on a UP-aware kernel and see if this could be reduced by flushing when a vCPU is migrating to another physical CPUs.
References: http://lists.xen.org/archives/html/xen-devel/2016-04/msg03157.html