Monday, June 26th 2017

Critical Flaw in HyperThreading Discovered in "Skylake" and "Kaby Lake" CPUs

A critical flaw was discovered in the way Intel implemented its simultaneous multi-threading technology, HyperThreading, on "Skylake" and "Kaby Lake" processors. Being a micro-architecture specific flaw, this could affect all implementations, from low-power mobile chips, to mainstream desktop, high-end desktop, and perhaps even enterprise-segment Xeon processors. At this time, there are no security implications of this flaw.

Intel chronicled this flaw in its micro-architecture errata "SKZ7/SKW144/SKL150/SKX150/SKZ7/KBL095/KBW095," and described it as follows: "Under complex micro-architectural conditions, short loops of less than 64 instructions that use AH, BH, CH or DH registers as well as their corresponding wider register (e.g. RAX, EAX or AX for AH) may cause unpredictable system behavior. This can only happen when both logical processors on the same physical processor are active." As an implication, Intel goes on to note that Due to this erratum, the system may experience unpredictable system behavior."
The HyperThreading flaw can be fixed through a micro-code update distributed as a UEFI firmware update. Typically, it becomes the responsibility of DIY PC motherboard, pre-built desktop, and notebook manufacturers, to distribute the update. The issue first came to light in a Debian Linux user mailing-list, although it affects all PC operating systems, not just Linux. Support groups of Debian recommend disabling HyperThreading in the UEFI setup programs of your computers as a temporary workaround, till the micro-code patch is applied. Disabling HyperThreading will reduce performance in multi-threaded apps. Source: Debian Mailing List
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98 Comments on Critical Flaw in HyperThreading Discovered in "Skylake" and "Kaby Lake" CPUs

#76
Dave65
Hard to believe Intel has gone from top dog to not knowing 3+3..
This is what happens when you sit on your FAT CAT ass in your ivory tower.
Posted on Reply
#78
R-T-B
Liviu Cojocaru
I just hope this will get a fix soon.
It will. All these types of bugs are common to most complex CPUs (the only thing that really varies is severity), and will be fixed via microcode, which is literally microcodes purpose people. The only thing you have to do is wait for the vendor of your mobo to get onboard, or use a tool to patch your bios if they never do. Look up UBU (Universal Bios updater)
Posted on Reply
#79
notb
Dave65
Hard to believe Intel has gone from top dog to not knowing 3+3..
This is what happens when you sit on your FAT CAT ass in your ivory tower.
In the meantime Intel is fixing this issue pretty much instantly, while the infamous FMA3 Ryzen bug was addressed by AMD after... 3 weeks?
It's still the company that makes stuff that "just works". The stuff that you don't have to think much about.
As time goes by and I read all these Ryzen threads, I think this is the actual problem. Intel CPUs are too easy. They don't give "PC tweaking enthusiasts" enough thrills and adrenaline.
trparky
YES! It's always been that way. We are a different breed after all. Always tweaking, always pushing our systems just a little bit further to eek out just a little bit more performance. It's been that way for as long as I can remember. There's wouldn't be sites like this site and others like it if it weren't for people wanting to do just that.
It hasn't been like that at all. Building and tweaking computers in the past was about overcoming actual problems. CPUs were slow, RAM was tiny and so on.
Not so long ago people were building home-made water-cooling solutions using parts from DIY home improvement stores (gardening hoses etc) That was risky. Sure, some did it for fun, but it was often important for the whole community.
Also OEM stuff was hugely expensive and acceptable notebooks were for the rich.

It's so much different today. First of all: you can simply buy a notebook and get a life. But even if you stay with custom desktops, it's so easy. And second: because PCs got so powerful, overclocking/tweaking is almost pointless.

Generally speaking, being fascinated by PC building early in life is fairly normal. We've all been there. But at some point people simply learn to use PCs, not just build and tweak them. There's so much more in computing than just building the tool.
Posted on Reply
#82
hat
Enthusiast
notb
In the meantime Intel is fixing this issue pretty much instantly, while the infamous FMA3 Ryzen bug was addressed by AMD after... 3 weeks?
It's still the company that makes stuff that "just works". The stuff that you don't have to think much about.
As time goes by and I read all these Ryzen threads, I think this is the actual problem. Intel CPUs are too easy. They don't give "PC tweaking enthusiasts" enough thrills and adrenaline.

It hasn't been like that at all. Building and tweaking computers in the past was about overcoming actual problems. CPUs were slow, RAM was tiny and so on.
Not so long ago people were building home-made water-cooling solutions using parts from DIY home improvement stores (gardening hoses etc) That was risky. Sure, some did it for fun, but it was often important for the whole community.
Also OEM stuff was hugely expensive and acceptable notebooks were for the rich.

It's so much different today. First of all: you can simply buy a notebook and get a life. But even if you stay with custom desktops, it's so easy. And second: because PCs got so powerful, overclocking/tweaking is almost pointless.

Generally speaking, being fascinated by PC building early in life is fairly normal. We've all been there. But at some point people simply learn to use PCs, not just build and tweak them. There's so much more in computing than just building the tool.
Personally, tweaking is all the same for me. Sure hardware is just better these days, but the principle remains the same for me today as it was back then: to get more performance by applying some tweaks. Maybe catch up to the performance of a more expensive option by buying a cheaper option and tweaking it. Unfortunately the second part of that is one foot in the grave these days with the way things have been getting locked down... especially by Intel.
Posted on Reply
#83
trparky
hat
getting locked down... especially by Intel.
That's why we have to support those companies like AMD that allow for freedoms like unlocked multipliers.
Posted on Reply
#84
hat
Enthusiast
I'm sure if it was the other way around, AMD would have locked theirs down too. They're not some knight in shining armor, they're just the underdog. Intel's been comfortably on top for way too long and it shows.
Posted on Reply
#85
Liviu Cojocaru
R-T-B
It will. All these types of bugs are common to most complex CPUs (the only thing that really varies is severity), and will be fixed via microcode, which is literally microcodes purpose people. The only thing you have to do is wait for the vendor of your mobo to get onboard, or use a tool to patch your bios if they never do. Look up UBU (Universal Bios updater)
Is the problematic code specific to a certain application?

The only crashes that I get (rarely) are in Battlegrounds but I don't think it has anything to do with this problem
Posted on Reply
#86
R-T-B
Liviu Cojocaru
Is the problematic code specific to a certain application?

The only crashes that I get (rarely) are in Battlegrounds but I don't think it has anything to do with this problem
I doubt any code that is compiled succesfully will actually produce any kind of problem. It would have to be intentional malware of some type to exploit this (if that is even possible).
Posted on Reply
#87
bug
Liviu Cojocaru
Is the problematic code specific to a certain application?

The only crashes that I get (rarely) are in Battlegrounds but I don't think it has anything to do with this problem
Come on, dude. The problem is described in Debian's own announcement: https://lists.debian.org/debian-devel/2017/06/msg00308.html (I hope you're not too lazy to scroll down).
But even without that, when was a firmware bug specific to an application?
Posted on Reply
#88
Aquinus
Resident Wat-man
Liviu Cojocaru
Is the problematic code specific to a certain application?
You could always read the announcement:
One important point is that the code pattern that triggered the issue in OCaml was present on gcc-generated code. There were extra constraints being placed on gcc by OCaml, which would explain why gcc apparently rarely generates this pattern.
Posted on Reply
#89
Liviu Cojocaru
bug
Come on, dude. The problem is described in Debian's own announcement: https://lists.debian.org/debian-devel/2017/06/msg00308.html (I hope you're not too lazy to scroll down).
But even without that, when was a firmware bug specific to an application?
Dude, I did not ask you to do anything. You're not obligated to give me any kind of information...It was just a simple question, if you're frustrated in any way that is not my problem ;) I did not have time to read that article yet and yes I know a firmware bug is not specific to an application but the application itself might be vulnerable to that code
Posted on Reply
#92
Dave65
notb
In the meantime Intel is fixing this issue pretty much instantly, while the infamous FMA3 Ryzen bug was addressed by AMD after... 3 weeks?
It's still the company that makes stuff that "just works". The stuff that you don't have to think much about.
As time goes by and I read all these Ryzen threads, I think this is the actual problem. Intel CPUs are too easy. They don't give "PC tweaking enthusiasts" enough thrills and adrenaline.

It hasn't been like that at all. Building and tweaking computers in the past was about overcoming actual problems. CPUs were slow, RAM was tiny and so on.
Not so long ago people were building home-made water-cooling solutions using parts from DIY home improvement stores (gardening hoses etc) That was risky. Sure, some did it for fun, but it was often important for the whole community.
Also OEM stuff was hugely expensive and acceptable notebooks were for the rich.

It's so much different today. First of all: you can simply buy a notebook and get a life. But even if you stay with custom desktops, it's so easy. And second: because PCs got so powerful, overclocking/tweaking is almost pointless.

Generally speaking, being fascinated by PC building early in life is fairly normal. We've all been there. But at some point people simply learn to use PCs, not just build and tweak them. There's so much more in computing than just building the tool.
Your fanboiism runith over:roll:
Posted on Reply
#93
trparky
notb
Generally speaking, being fascinated by PC building early in life is fairly normal. We've all been there. But at some point people simply learn to use PCs, not just build and tweak them. There's so much more in computing than just building the tool.
OK, so we're not laying down circuits, we're not soldering, etc. but we are building with our own two hands. There's just something to be said about building something with one's own hands. It's just like how some people are into cars and rebuilding old classics. When I build my own PC and it passes POST for the first time there's an exhilarating feeling.

I just recently got into overclocking. I have an older Core i5 3570K CPU that for the longest time I ran at stock speeds. I know, what a waste! But I managed to overclock this beast of a chip to 4.4 GHz, that's 1 GHz faster than stock! It's like it's a free upgrade! Hell, on some benchmarks I'm running faster than a Core i5 6600K. I don't know about you but that's impressive! The fact that a nearly five year old chip is beating out a chip that's just over a year old is impressive as all hell. Would I be able to do this on an OEM machine? Would I be able to tweak the hardware this much and be able to get an upgrade without spending a dime? Nope.

You're not going to change my mind on building one's own PC. There's just something about building your own PC along with the fact that you know each and every part in it are premium components.
Posted on Reply
#94
RealNeil
So the fix for these CPUs will come included in a Mainboard BIOS update?
Posted on Reply
#96
notb
Dave65
Your fanboiism runith over:roll:
Fanboyism of what? OEM PCs? Not worrying about the hardware too much? :)

trparky
OK, so we're not laying down circuits, we're not soldering, etc. but we are building with our own two hands. There's just something to be said about building something with one's own hands. It's just like how some people are into cars and rebuilding old classics. When I build my own PC and it passes POST for the first time there's an exhilarating feeling.
Most people don't get this "feeling".
And the inevitable car analogy has arrived - OK. So lets just assume that a "car enthusiast" likes to tinker etc.
But you don't have to be a "car enthusiast" to be a "driving enthusiast".
But we don't have such an easy separation with computers. You call yourself an enthusiast because you like assembling them. I call myself an enthusiast because I like using them. There isn't a good word for this. I'm a computation enthusiast. I'm a simulation enthusiast. I'm a programming enthusiast. I used to be a gaming enthusiast. You can do many things with a computer, so using a wrapper "computer enthusiast" is very practical.
Am I an assembly/OC enthusiast? Not any more. This part of my life ended 10-15 years ago (when I was a teenager).

trparky
I don't know about you but that's impressive!
How is that impressive? It's just numbers. Did your performance get a boost? What about temperature and power draw? Do you need this boost or are you doing this for fun?
I used to OC a lot back in the Athlon days, but I never did it for fun. I was a teen, I couldn't afford an expensive CPU. I got a cheap one and OC it, because that actually made a difference (whether I would be able to play games I want or not).
trparky
Would I be able to do this on an OEM machine? Would I be able to tweak the hardware this much and be able to get an upgrade without spending a dime? Nope.
I don't know what you're doing for a living. Is it building PCs? :)
Lets say someone is a solid state physicist. He simulates graphene solutions to find new ways to use this material. Can he do this on an OEM machine? Yes. Can he have fun? Yes.
Imagine someone is a neurosurgeon. He uses his PC to watch porn. Can he do this on an OEM machine? Yes. Can he have fun? Yes.

You see? There's more to PCs than just watching benchmarks.
trparky
You're not going to change my mind on building one's own PC. There's just something about building your own PC along with the fact that you know each and every part in it are premium components.
I'm not trying to change your mind on anything. I'm trying to add some sensibility to this discussion. :D
BTW: Don't live with an impression that parts put in OEM workstations are of lesser quality than those "premium" stuff you can buy yourself. OEM desktops are often beautifully designed: small, very quiet, very stable and very long-lasting. They don't have LEDs and trendy brand logos, but they have quality circuitry and cooling.
Posted on Reply
#97
EarthDog
trparky
OK, so we're not laying down circuits, we're not soldering, etc. but we are building with our own two hands. There's just something to be said about building something with one's own hands. It's just like how some people are into cars and rebuilding old classics. When I build my own PC and it passes POST for the first time there's an exhilarating feeling.

I just recently got into overclocking. I have an older Core i5 3570K CPU that for the longest time I ran at stock speeds. I know, what a waste! But I managed to overclock this beast of a chip to 4.4 GHz, that's 1 GHz faster than stock! It's like it's a free upgrade! Hell, on some benchmarks I'm running faster than a Core i5 6600K. I don't know about you but that's impressive! The fact that a nearly five year old chip is beating out a chip that's just over a year old is impressive as all hell. Would I be able to do this on an OEM machine? Would I be able to tweak the hardware this much and be able to get an upgrade without spending a dime? Nope.

You're not going to change my mind on building one's own PC. There's just something about building your own PC along with the fact that you know each and every part in it are premium components.
Thats an about face from calling OEM PCs 'shit' as you originally did. Your opinion is like wallpaper...changes with the time... lolol! First they were poop, now the reason changes to accomplishment of building something with your hands when everyone challenged that 'poop' notion. Its ok to say we are wrong at times. :)
Posted on Reply
#98
trparky
notb
How is that impressive? It's just numbers. Did your performance get a boost? What about temperature and power draw? Do you need this boost or are you doing this for fun?
Yes, it actually did help performance!!! Loading up a virtual machine under this current overclock no longer lags the host OS as badly as it once did. The host OS remains pretty damn close to regular performance even with the VM running whereas before the overclock the system was clearly showing signs of struggling under the load.

I use virtual machines to test software before I install it on the host OS. It's much easier to just create a VM snapshot and restore back to it than to have to reload the host OS because the uninstall routine screwed something up. I also use VMs to test freeware software that I develop to make sure that it runs on every version of Windows going back to Windows 7 since I use Windows 10 as my daily running OS.

EarthDog
Thats an about face from calling OEM PCs 'shit' as you originally did.
OK, so I went overboard with my "OEM PCs are shit" comment. There! I said it. However there are times when you can build a computer yourself for less than if you were to go with an OEM system since they generally charge more for their more enthusiast systems. If you want an SSD in an OEM system be prepared to pay more than if you were to buy an aftermarket SSD. Same goes with if you want a gaming video card in it, be prepared to pay far more than if you were to buy an aftermarket card and while you're at it you'll more than likely have to replace the PSU since most OEM systems come with PSU that are just enough to run the core hardware and nothing added onto it. Do all of this stuff and you basically just voided the OEM warranty.
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