- Maybe I should buy an Intel system again because of the performance counters and other nice things.
Another Intel attack surfaces
- Yep, I shall go AMD this time...
From 2 days ago, in case you weren't aware.
itself it's not a problem but if you pair it with something else it destroys a major line of defense against that something else.
AMD is still architecturally vulnerable to some variants of SPECTRE, they just consider it "hard to exploit", but they do recommend you run KASLR to harden against it. Well, so much for that.
It works pretty well against remote code execution because it's hard for an attacker who can't already execute arbitrary code on your machine to determine the address space layout. In principle it can also be used to protect the kernel against user processes, but that's much harder because a process that can already execute arbitrary user code on the same machine can use a variety of side channel attacks like this to determine the kernel address space layout.
KPTI was originally proposed to close some of those side channels, but it's kind of expensive. It only got enabled by default (on Intel) because it also mitigates Meltdown, which is a much worse problem. It also doesn't handle all of the side channels:
http://www.cs.ucr.edu/~nael/pubs/micro16.pdf
Meanwhile, if some kernel code is vulnerable to Spectre (i.e. the Spectre mitigations are not implemented properly), it could allow the attacker to read arbitrary kernel memory. That is obviously very bad, but the ability to read arbitrary kernel memory implies that the attacker can already determine the kernel address space layout, so I'm not sure how KASLR would be helpful in mitigating that.
No, it's a misunderstanding to say that the flaw in the "Take A Way" whitepaper depends on a mechanism already patched. Attack scenarios which are used in the paper to show the feasibility of the 2 new side channels are patched (except the KASLR entropy reduction), but the side-channels themselves are not patched.
And might never be patched just like FLUSH+RELOAD never was. And the paper itself even points out that FLUSH+RELOAD is a more applicable attack than Load+Reload is:
> Comparison with Flush+Reload. While Flush+Reload invalidates a cache line from the entire cache hierarchy, Load+Reload only evicts the data for the sibling thread from the L1D. Thus, Load+Reload is limited to cross-thread scenarios, while Flush+Reload is applicable to cross-core scenarios too.
Collide+Probe is more interesting as it can use virtual address instead of physical address in comparison to Prime+Probe. That may get a microcode update to do a way flush on context switch as part of general Spectre mitigations (just like the branch predictors are), but it can also be handled entirely in software by adjusting how the AES implementation works as the paper also talks about.
But fundamentally what these attacks enable are super old & well known, with multiple existing mechanisms that fulfill similar roles. It's why Spectre/Meltdown never focused on the side-channel part of the attack, because it seems to just be assumed side-channels will always exist. And why the paper used existing, documented vulnerabilities to do the exploit side of their PoC, just changing the side-channel used to ex-filtrate the data.
Is there something particularly unique or severe about "Take A Way" other than techchrunch's bad reporting of it?
It still has to be published. The article doesn't claim to break all the isolation mechanisms of the processor like Spectre/Meltdown. Why should we compare this paper with Spectre/Meltdown?
> Is there something particularly unique or severe about "Take A Way" other than techchrunch's bad reporting of it?
Yes, there are at least three things in "Take A Way" which is interesting:
- These side-channels are harder to detect because it doesn't require a very intensive use of the cache (no flush / filling all cache ways / etc.). A single collision is enough to evict a targeted cache line.
- It allows to set up a covert channel that can transfer up to 588.9 kB/s.
- They did a reverse engineering job on a processor mechanism and its undocumented hash function.
That was sort of my point, we shouldn't be making that comparison but further up in the comment chain that's exactly what was being done.
The paper itself is great and definitely should exist. But it's not a counter-argument to "yet another Intel attack surfaces" either.
Except there is. Hence why Skylake suffered from Meltdown while AMD didn't. Skylake's design is to do ACL checks at instruction retirement instead of up front. AMD's is the reverse.
Software workarounds for Meltdown exist, yes, but the Skylake architecture still fundamentally has that insecure design.
It bothers me and I don’t really understand. There are some really vile comments about Intel and unreasonable praise for AMD - simply because it’s the “underdog”. What is this? Some kind of a sport that one is rooting for the “underdog”. It’s a multi billion dollar corporation.
I should clarify that my frustration isn’t about what the OP said. It’s a general observation.
What gave you that idea? This thread was clearly about someone building a local PC. There's no reason to assume that'd be a server chip?
But even in the server world go look up any comparison of Epyc Rome vs. Intel Xeon and you'll still struggle to find a reason to go Intel. The Epyc 7742 is in a league of its own at this point.
This entire post is about Intel security flaw where we just had one discovered for AMD yesterday! But people are not as vile about AMD but become hostile when it comes to Intel. Why? There are some toxic people defending both sides with passion. I’m baffled. If this isn’t “Fanboys”, what is?
Regarding comparisons, I’m yet to see a conclusive source that points at AMD > Intel for server workloads - benchmarking these things is complex. Power, efficiency, workload types, etc matter. So it’s not as simple as saying “Hey, AMD won”.
I’m disappointed at the hostility for pointing out fanboyism on HN. It’s present whether one denies it or not.
Edit: Holyshit. I won’t be responding anymore. This has become an unproductive discussion simply for pointing out the bias in supporting the “underdog”. I have no way to prove this but I stand by my observations and what my eyes see - given Apples and Apples comparison for metric X or security flaw X, people have a deep bias for supporting the “underdog”. I saw this first hand back in 2006 when Intel was the “underdog”. This is a fact and no amount of massaging on HN or the Internet forums will change that. I’m again disappointed in the HN community’s response.
I work as an HPC administrator and I just want to tell a single thing:
We were unable to buy first generation EPYC processors because almost all of the production run is bought by Google, Amazon and Dropbox. They weren't offered by many vendors as general availability servers because it wasn't possible.
It's a bit late here so, I cannot do much research but I'll leave this Phoronix article [0] about RocksDB performance.
Phoronix Test Suite sounds a bit cheesy but, as far as I can see, it's becoming a reputable benchmark suite. I was troubleshooting a server from a big manufacturer and, its official live CD has this thing installed to see how system performs.
Also our fellow HPC centers says that EPYC is not vaporware in terms of performance.
[0]: https://www.phoronix.com/scan.php?page=article&item=intel-am...
Because it very much comes across as though you've got an axe to grind. OP was "maybe sort of" going to build an AMD box, for which there are a lot of good reasons irrespective of the bug on topic, and this set him over the top.
His post doesn't really exude fanboy behavior, and your comment - while possibly appropriate for some other post - isn't really appropriate to OP.
AMD's was a new side channel that doesn't appear to be that different from existing side channels like flush+reload. Some pros (and cons) over the established ones, but you're not attacking anything with those either. It's how you ex-filtrate data after a successful attack.
This, by comparison, is a new attack vulnerability. They are different severity, and I'd expect here of all places to recognize & acknowledge that. I'm baffled as to why you seem to be expecting something different?
> Regarding comparisons, I’m yet to see a conclusive source that points at AMD > Intel for server workloads - benchmarking these things is complex. Power, efficiency, workload types, etc matter. So it’s not as simple as saying “Hey, AMD won”.
Did you look? Yes benchmarking these is complex, but when one CPU wins the overwhelming majority of every comparison on every metric it reeks of fanboyism to then claim it's "not conclusive." There's no shortage of server CPU benchmarks done in this space. If you have a specific comparison that's missing then say it. Otherwise you're just accusing people of the fanboy behavior that you're exhibiting.
But here: https://www.anandtech.com/show/14694/amd-rome-epyc-2nd-gen/1...
"For those with little time: at the high end with socketed x86 CPUs, AMD offers you up to 50 to 100% higher performance while offering a 40% lower price. Unless you go for the low end server CPUs, there is no contest: AMD offers much better performance for a much lower price than Intel, with more memory channels and over 2x the number of PCIe lanes. These are also PCIe 4.0 lanes. What if you want more than 2 TB of RAM in your dual socket server? The discount in favor of AMD just became 50%.
So has AMD done the unthinkable? Beaten Intel by such a large margin that there is no contest? For now, based on our preliminary testing, that is the case. The launch of AMD's second generation EPYC processors is nothing short of historic, beating the competition by a large margin in almost every metric: performance, performance per watt and performance per dollar."
Like every review of Rome is like this. AMD released an incredible product. Credit where credit is due is not fanboyism.
Referring to people as "fanboys" is one of them. There's a reason for this: it's an insult, for starters. Furthermore, it leads to unproductive discussions. More heat than light.
There's almost always a way to express yourself that doesn't involve being dismissive and insulting. You may not realize that's what you're doing by saying "fanboy". But it is what you're doing.
If you'd pulled a highfalutin' word like "partisanship" you would probably find a productive conversation. Just avoid fanboy, circlejerk, and other obvious flamebait, and you'll be fine.
The schadenfreude isn't coming from nowhere.
You can just flip the sides, if AMD controlled 85% market share, the shareholders would demand the same unless we have laws preventing anti-competitive behavior.
That said, I do acknowledge the business leadership at Intel and their toxic attempts to prevent competition.
Legislation has nothing to do with "underdog" or marketshare. It has to do with anti-competitive practices regardless of the party. The same laws would apply to Intel or AMD regardless of their market share.
and people who bought AMD stock, but none of Intel or anything much else, because they see the CPU market as a 0 sum game. AMD was a darling of first time investors on a certain platform and they don't diversify. It’s not that their constant wall of pro-AMD stock noise is going to affect the stock price, but it also becomes a bit of an emotional thing for them.
All the AMD posts here end up looking a lot more like Reddit than Hacker News
HN is not exactly the source of truth for anything technical, but generally people are either in the ballpark on technical comments, or (more likely) get corrected by someone who is.
On AMD posts that doesn’t happen and it just becomes a low quality cesspool of “I just bought a gaming PC and chose AMD”, “Intel is on life support right now omg”, and a few poorly supported rationalizations of the post's topic.
And when you call it out these people assume you’re defending Intel (because to them it’s a holy war)
I consider AMD for its new Infinity Fabric and multi-core performance. I also use performance counters a lot to optimize my code and improve my understanding of modern processors even further.
This will be my 5th build and I've built 2 AMD and 3 Intel systems for long-term use in a span of ~20 years. I think it's logical to go for a high-performance system with lower attack count/surface to reduce the chance of getting performance-crippling uCode or Kernel patches in the future.
I was probably a fanboy while overclocking my 1433MHz 1700+ to 2.2GHz with ABIT ultra mother boards. These days and mindset has long gone, at least for me.
OTOH, I have more than enough cutting edge hardware from major vendors to manage and play with. So, I'm not hungry for anything really.
I also did root for AMD when I was younger however, in a more down-to-earth fashion. AMD was providing 90% of the performance of a comparable Intel system and, Intel was so dominating that AMD was at the brink of collapse.
I rooted for AMD because I wanted them to survive. I wanted competition. I wanted to see more interesting ideas from more vendors. I also reacted to that infamous "AMD's thermal management doesn't work" video from Tom's Hardware because my and my friends' AMD systems' thermal management features were working fine.
I rooted for AMD because they were more dynamic when compared to Intel. They allowed overclocking, experimenting. They had more chipset choices and some of these chipsets did interesting things that Intel was not daring to try.
Intel was a company wearing suits even in weekends, while AMD was going to work putting on jeans and, it was exciting for young enthusiasts.
AMD still has this in its gene though. They were kind and open enough to revise their GPU silicon to enable truly open source drivers sans HDCP. Their company culture is different and I root for the underdogs sometimes because, I root for competition.