The Brutal Performance Impact From Mitigating The LVI Vulnerability

[numacross]

Dug into SGX a bit... It's a fairly new set of instructions and it doesn't seem that AMD even has them... And seems to only be useful in certain circumstances... As bad as the performance hit is... Is this ultimately a big deal? I'm not sure that it is. These mitigations should only be needed if and where SGX instructions are being used?

SGX is used in supposedly high security environments like Neflix 4K DRM on Windows, playing 4K Blurays and so on. For most people it can be safely disabled in BIOS. I think Intel is at their 28th try of getting SGX into Linux kernel so support of it under Linux is probably non-existent.

The more or less comparison to TSX quoted above is valid I think. It seems Intel has a habit of creating new instruction sets that come with insecurity vulnerabilities... TSX has been a problem since it was introduced with Haswell before the speculative execution exploits were discovered.

The idea behind TSX is very nice and has huge benefits when used correctly (I think some older console emulator had a huge boost because of it), but it was very buggy and had to be disabled by microcode on Haswell altogether.

[Jumbotron]

Bulldozer has always been an elegant design. I am frustrated that AMD had to scrap it and go copy Intel's SMT design. Now Zen is just a me-too Core architecture with slightly worse IPC but more cores per dollar.

But hey, people cared about their "single threaded performance" AKA "muh garbage single threaded vidya gamez". Oh, and superpi, that's terribly important apparently.

I hope now that AMD begins enjoying a dominant position in the market, they can finally implement the plan of plenty tiny integer cores with plenty of large gpgpu cores, and HSA. It will be glorious.

I completely agree. My Bristol Ridge A12-9800 APU in my desktop and Bristol Ridge A12-9700P APU in my laptop ( Both are Excavator based upgrades to Bulldozer and also Carrizo process upgrades ) have been wonderful since 2016. Stable, fast, performant over time especially with constant updates from Mesa and AMDGPU along with general performance improvements with new Linux kernels. Yeah...it kind of sucks that the cores share an FPU but I get at the time why AMD engineers went with a "Clustered-Multi-threaded" architecture. It's simpler and more integer based. Now, in hindsight, the Bulldozer family, particularly the Excavator improvement which was the last improvement following Piledriver and Steamroller is not such a dog compared to similar generation Intel CPU's once you apply ALL the various mitigations....which I'm sure more are coming for Intel chips.

[Jumbotron]

Bulldozer has always been an elegant design. I am frustrated that AMD had to scrap it and go copy Intel's SMT design. Now Zen is just a me-too Core architecture with slightly worse IPC but more cores per dollar.

But hey, people cared about their "single threaded performance" AKA "muh garbage single threaded vidya gamez". Oh, and superpi, that's terribly important apparently.

I hope now that AMD begins enjoying a dominant position in the market, they can finally implement the plan of plenty tiny integer cores with plenty of large gpgpu cores, and HSA. It will be glorious.

And to your last point with AMD hopefully implementing "plenty tiny integer cores with plenty of large gpgpu cores, and HSA. It will be glorious". I look forward to that as well. However I think at this time HSA has stalled. Excavator based cores such as Carrizo and Bristol Ridge are full HSA 1.0 compliant. But extending HSA from CPU to dedicated GPU on PCIe seems to have really gone nowhere. That could be changing. By the time the Zen 4 CPU's come out along with Navi 2 refresh AMD will unleash their 3rd generation of Infinity Fabric which will fulfill the promise all the years ago when AMD introduced the concept of "Fusion" which ultimately led to "HSA". One could make a hand waving argument that Infinity Fabric is the ultimate and final pinnacle of the "AMD Fusion" vision which was introduced in 2006 not long after AMD bought ATI that year.

[numacross]

And to your last point with AMD hopefully implementing "plenty tiny integer cores with plenty of large gpgpu cores, and HSA. It will be glorious". I look forward to that as well. However I think at this time HSA has stalled. Excavator based cores such as Carrizo and Bristol Ridge are full HSA 1.0 compliant. But extending HSA from CPU to dedicated GPU on PCIe seems to have really gone nowhere. That could be changing. By the time the Zen 4 CPU's come out along with Navi 2 refresh AMD will unleash their 3rd generation of Infinity Fabric which will fulfill the promise all the years ago when AMD introduced the concept of "Fusion" which ultimately led to "HSA". One could make a hand waving argument that Infinity Fabric is the ultimate and final pinnacle of the "AMD Fusion" vision which was introduced in 2006 not long after AMD bought ATI that year.

You mean Infinity Architecture?

[Jumbotron]

You mean Infinity Architecture?

Yes...but Infinity Fabric as outlined and introduced by Mark Papermaster in 2017 is the basis for the larger framework of Infinity Architecture.

https://en.wikichip.org/wiki/amd/infinity_fabric

Posted by
u/negligible-function
2 years agoAMD CTO Mark Papermaster reveals interesting details of Infinity Fabric and how AMD's current and future products benefit from it.


News
The original article in Japanese can be found here: http://pc.watch.impress.co.jp/docs/c...i/1053318.html

This is a Google translated version: https://translate.google.com/transla...-text=&act=url

TLDR:

• All Zen and Vega CPUs, GPUs and APUs are build on top of the Infinity Fabric foundation.
• Inifinity Fabric is very flexible in terms of implementation. While the logic layer remains constant the physical layer can change wildly.
• Performance scales linearly up to 64 cores.
• The Infinity Fabric configuration of mobile Ryzen is significantly different from desktop Ryzen.
• Thanks to Infinity Fabric Raven Ridge APUs will get rid of the hassle of having one dedicated memory bus for the CPU and another one for the GPU.
• Infinity Fabric flexibility allows it to scale very well from on-die to off-die. It will even be used to interconnect Naples sockets on top of 64 PCIe links.
• Infinity Fabric will remain a proprietary technology in order to allow AMD to change it as they see fit. AMD will create the required interfaces and licensing to allow other companies to integrate their products with it.
• Unlike Intel with its Omni-Path AMD is embracing open standards for HPC interconnects therefore AMD will not extend Infinity Fabric to that level and will instead use Gen-Z and CCIX.

25 comments

[Jumbotron]

You mean Infinity Architecture?

Yes.... but Infinity Fabric is the basis for the larger framework of Infinity Architecture. As Infinity Fabric is a superset of HyperTransport and Infinity Architecture will bring out the ultimate fruition of the AMD "Fusion" vision from 2006 as it was later coalesced into the HSA movement, one could say that Infinity Architecture is the ultimate realization of HyperTransport and HSA together and synthesized at the system level.

[creative]

Looks like I switched to a 3600 just in time. Not a week too late.

Intel = Very rusty and falling apart architecture.

It took a while for it to sink in for me. Back to good old AMD and its own issues. At least AMD's issues are not of such epic proportion this go round.

Update: I would like to note that as of now I have not really had much issue with AMD's new platform. My first impression after having my new rebuild up and running was; This feels and runs like Cadillac or Benz as far as a system goes. Of course I got the system later after some things have gone through some maturing.

AMD = The new high end and quality user experience standard and I really do believe stuff is only going to get better and faster.

[creative]

Some have speculated that intel is ten years behind AMD cause their architecture is so superfluous that they can barely grasp the concept of new design or redesign.


I was on an i7 for 3 years and enjoyed it but did not know how bad intels tech was until roll out, after roll out of vulnerabilities.


Four words... Intel recovery support groups—yes I think those are going to be a thing.


Him.."I can't believe I was so blind" Her.... "Its ok, its ok to like AMD again, we all have had to go through this, I was in denial too"...

[bug77]

Try to tell that you your body, while facing COVID-19,...

Not an issue, 95% of the patients only develop mild reactions

[areilly]

Sucks to be trying to sell "hostless lambdas" or whatever the cloud geeks think is cool at the moment, and it seems that running contemporary JavaScript on the same machine that handles your secrets and does your real work might not be such a good idea, but I don't think that this is the end of the world. The problem, such as it is, arises from letting malicious code share hardware that has lots of hidden (non-architectural) state, (because it turns out not to be very well hidden). Seems obvious that rather than slowing the machine down by orders of magnitude, by preventing any of that hidden state from doing its job, the much better approach would be to just keep the malicious code somewhere more isolated, where it can't see the hidden state of other code. That may require operating system changes, so that task switches don't just swap visible register state, but do some more work to flush that hidden state, at least when switching between different "trust" domains. That is: you can separate in time, and you can separate in space. Modern processors are growing cores like rabbits (those new Amazon Graviton2, for example: 64 single-threaded cores) so much more often threads will not have to time-slice at all, they'll just spin up another core and own it for the duration.

Oh, and the good old rule of not running malicious code in the first place seems like a keeper, too. Besides sticking with open source, and being careful around the trust of your sources when you can't. Surely it's not beyond the wit of man to detect code that spends a lot of cycles doing nothing obviously useful while looking at the high-res clock, and just knocking it on the head? Perhaps deciding that an advertising-sponsored browser plugin or mobile app might not be a great idea after all?