[vfio-users] Regarding ACS support

[Zir Blazer]

I don't have any type of Blogger account to post a comment here:http://vfio.blogspot.com.ar/2015/10/intel-processors-with-acs-support.html
So instead I drop an E-Mail.

All the LGA 2011 (Sandy Bridge-E, Ivy Bridge-E) and LGA 2011-3 (Haswell-E and next to come Broadwell-E) Core i7s are actually rebranded Xeons E5, they're based on the same physical dies. Its not surprising that they have ACS, but more that Intel did not disable it in these parts. As LGA 2011 Core i7 are a subset of Xeons E5, Xeons E3 are pretty much a superset of consumer LGA 1155/1150/1151 Core i5/i7 (They also use the same dies), that's why they don't support ACS.Skylake-E is supposedly for 2017. The -E platform is usually a generation or two behind the consumer one, only during the initial Sandy Bridge generation and the recent Haswell era you had consumer and enterprise platforms with the same CPU architecture. Now you have consumer Skylake and enterprise Haswell-E, once again, a two generation gap.

The latest Xeons E3 V5 Skylake has also been recently released:
http://www.cpu-world.com/news_2015/2015102001_Intel_Greenlow_platform_and_Xeon_E3-1200_v5_series_launched.html
I DO NOT suggest to get one right now since Intel "forgot" to enable a feature, SGX, and you need to wait for a new Stepping for it:
http://www.cpu-world.com/news_2015/2015100301_Intel_to_enable_Software_Guard_Extensions_on_Skylake_processors.htmlAlso, there are claims that Intel has limited Xeons E3 V5 with consumer Motherboards and that you CANNOT USE them in non-C Chipsets. They will not boot based on published tests. So if you want the new Xeons E3 V5, you need a true Server or Workstation Motherboard. May as well use them with DDR4 Unbuffered + ECC RAM.


Should you want LGA 2011-3, check the full Processor list here:
https://www.pugetsystems.com/labs/articles/Intel-CPUs-Xeon-E5-vs-Core-i7-634/
Besides the standard Core i7 5820K, you also have the Xeon E5-1620V3. It is an actually interesing Processor since it works more as an entry level alternative. It is a humble Quad Core and it cost around 300 U$D, while the Core i7 5820K has 6 Cores but cost 400 U$D. The Xeon has also the full 40 PCIe Lanes while the 5820K is the only model to have 28 (Since Intel had to artificially differenciate it from the Ci7 5930K, causing that due to a single model in the entire LGA 2011-3 lineup, you have Motherboards Manuals that needs to specify what PCIe Slots and features works or not depending on if you use a Ci7 5820K or anything else). Also, at 300 U$D, the Xeon E5-1620V3 is around the cost of the LGA 1150 Xeon E3-1246V3/Core i7 4790 Haswell, and specs are also around the same, so expect that type of performance.
With XenGT and KVMGT coming (Renamed to Intel GVT-g), a very important thing is that LGA 2011 based Processors do NOT have integrated GPU. You will have to choose between having 4+ Cores with ACS support or GPU virtualization of the IGP. Xeons E3 with no IGP (Like the Xeon E3-1241V3) are excluded for obvious reasons, and since Intel seems to price the IGP versions around 20 U$D or so more than the IGP less ones, it is rather stupid to NOT purchase the models with IGP considering that KVMGT could be a killer feature. 		 	   		  
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