AMD Details "SQUIP" Side Channel Vulnerability For Zen's Execution Unit Scheduler

[Alex/AT]

"constant-time algorithms" are now "best practices", oh really?
Data-independent random-time algorithms feel much more secure. You can't infer anything from a random time. The only thing we need is some 'RANDDELAY x,y' CPU command that uses software-independent entropy source to delay for some small amount of CPU cycles between x and y.

[geearf]

Because if you split them to seperate cores, your single threaded performance will be horrible. You want to have high single thread performance (by using multiple units for certain operations so if it is possible to execute few at once you can), but you also want to have good multicore performance and increase utilization of those units when they can't be used by 1 core.

This is whole paradox - if your workload can be perfectly parallel you would make as simple core as possible and make as many cores as possible. If workload is strongly bound by single thread you want as powerful single thread as possible - crank that GHz, make tons of execution/decoder units for 1 core etc.

This is a thing that if you want power saving processor, you want low frequency many simple cores with agressive downclocking.

Best gaming CPUs are exactly opposite of that.

I hope that Intel's aproach long term will good answear for that question, as Intel 12600k/12700k can compete with 5800X/5600X and if you pick non-K version efficiency is even better. Source:

https://www.techpowerup.com/review/intel-core-i5-12600k-alder-lake-12th-gen/20.html

E cores are more simple cores that take less die space and P-cores are those for single-threaded bound tasks.

Thank you for this explanation!

[archkde]

Ah. I think suspend being affected by SMT is firmware-related. I don't think it's a bug, but I'm curious on what exactly happens with SMT on/off in the firmware.

I have an ASUS PRIME-X470 PRO motherboard, and for the SMT option the BIOS specifically mentions S3/Sleep not functioning when cores are removed. In AMD CBS there's a similar note, and that implies whatever is happening is intentional and done by AMD.

The BIOS SMT option is not relevant here, Linux disables SMT by putting the extra logical CPUs into a deep idle state (C10) and never scheduling a task on or assigning an interrupt to them.

But from what I've found out by now, and unlike I had assumed, it's actually the kernel's job to restore the hardware state on resume from suspend. Firmware puts the CPU into the boot state. So this is actually a Linux kernel bug.

[PublicNuisance]

But how much performance did you lose in going back to a FX-9590? Did you "Before & After" benchmark your changes?

I haven't done any fresh ones but when I first bought the Ryzen 5 2600X years ago I saw most games give me at least a 20-30% jump over the FX-9590 with some even doubling. To be fair though at the time I didn't even know about stuff like the PSP and had I known I would never had bought the Ryzen. I would have instead spent my money on either a Libreboot or Coreboot solution. I'm trying to sell what parts I can now to move forwards in that direction and to also save up to get a Talos II. Gaming is my main hobby but I have to draw a line in the sand somewhere. From now on any hardware I buy has to obey some ground rules. No Intel ME or PSP that is not at least neutered in a FOSS fashion; No closed source BIOS; and compatible with the Libre kernel preferred.

[piotrj3]

What's the benefits of having those units in numbers bigger than 1 instead of just splitting them into separate cores? I assume you have different numbers for different types of units so that probably wouldn't really work out though.

Thank you!



Oh wow, is 8 the optimal number for most cases? Can you tweak it, whether in BIOS or on the fly, to a smaller number if it works out better?

Thanks!

Because if you split them to seperate cores, your single threaded performance will be horrible. You want to have high single thread performance (by using multiple units for certain operations so if it is possible to execute few at once you can), but you also want to have good multicore performance and increase utilization of those units when they can't be used by 1 core.

This is whole paradox - if your workload can be perfectly parallel you would make as simple core as possible and make as many cores as possible. If workload is strongly bound by single thread you want as powerful single thread as possible - crank that GHz, make tons of execution/decoder units for 1 core etc.

This is a thing that if you want power saving processor, you want low frequency many simple cores with agressive downclocking.

Best gaming CPUs are exactly opposite of that.

I hope that Intel's aproach long term will good answear for that question, as Intel 12600k/12700k can compete with 5800X/5600X and if you pick non-K version efficiency is even better. Source:

https://www.techpowerup.com/review/intel-core-i5-12600k-alder-lake-12th-gen/20.html

E cores are more simple cores that take less die space and P-cores are those for single-threaded bound tasks.

Yes, it's pretty easy to explain. When I suspend the system while some logical CPU is offline, the firmware will put that CPU in a very shallow idle state once the system resumes again. This leads to massively increased power usage. So I have a script that enables and immediataly disables SMT again on resume, which works around the bug because Linux puts the offline CPU in the deepest idle state properly.

Ah. I think suspend being affected by SMT is firmware-related. I don't think it's a bug, but I'm curious on what exactly happens with SMT on/off in the firmware.

I have an ASUS PRIME-X470 PRO motherboard, and for the SMT option the BIOS specifically mentions S3/Sleep not functioning when cores are removed. In AMD CBS there's a similar note, and that implies whatever is happening is intentional and done by AMD.

[fong38]

Sad thing is the fact your blinded to your own tribe. Your own community. The tribe of "non tribes." You all are united as a single tribe of being against tribes. You all have your own circle jerk.

The good old "lets pretend like everything in life is a circlejerk and I'm above it all"

It's like watching the "non fanboy" railing against amd while promoting only using Intel and Nvidia and will never use amd. It's hilarious. "Welp, it's bad to use amd, guess I'll use their competition instead." How convenient. Can hide being a fanboy while shilling for the other side

Not sure where you saw that in the thread? You can both be not loyal to multi billion dollar corporations and still use their products, you know.

Now I'm going to ignore this thread because I honestly don't want to see the level of mental gymnastics any responses will be by the non tribe, tribe, and non fanboy, fanboys.

"I'm right you're wrong and won't listen to any responses because I know I'm right" *plugs ears*

(Not sure if that post was meant as bait, if it was then I guess you got me.)

[middy]

I strongly disagree with that statement. Ideally all those companies have diffrent intend then you, they are not user friendly. So your intention is to not join any teams and just pick best tool for your job.

Like if you need open source driver for linux with wayland - you know where to go.
If you need scientific/high computation usage with CUDA - you also know where to go.
You need budget modern PC for general usage - you know also where to go.
You need rendering farm - you also know where to go.
You need higher stability platform that won't cause you USB dropout issues, or PCI-E you know who to pick.
You want a platform with better upgrade options long term you also know who to pick.

I had initially Ryzen 3600 (because back then it was good choice), and after I upgraded to Ryzen 5800X3D because it was good upgrade option for my platform. But if i buided PC from scratch I would actually go for something like 12600/12700 CPU.
I also have nvidia GPU because i do use CUDA/computationally intensive stuff.

Literally stop being fanboys. Pick what in right time best fits your usage.

Sad thing is the fact your blinded to your own tribe. Your own community. The tribe of "non tribes." You all are united as a single tribe of being against tribes. You all have your own circle jerk.

It's like watching the "non fanboy" railing against amd while promoting only using Intel and Nvidia and will never use amd. It's hilarious. "Welp, it's bad to use amd, guess I'll use their competition instead." How convenient. Can hide being a fanboy while shilling for the other side

"I'm against tribes so join me in my crusade against tribes" "I hate being a fanboy so join me in my hatred for one brand while promoting the other brand." God I love manipulation. Works wonders. Then you have the "I'm a fan of those against fanboys." You quite literally have people cheering on, being a fan for those who are against fanboys. The fanboys against fanboys. It's hilarious.

Now I'm going to ignore this thread because I honestly don't want to see the level of mental gymnastics any responses will be by the non tribe, tribe, and non fanboy, fanboys.

Birds of a feather flock together. People with similar beliefs, interest, anything that makes one person similar to another, will come together. Yes, even those that are against something, will unite together with others who against the same thing.

[DRanged]

What a fanboy, getting defensive because AMD can’t communicate or fix software issues. I owned a RX 5700 for 8 days and returned it with-in my return policy because I wasn’t going to get stuck with a non-functional GPU.

AMD’s windows drivers have always been garbage for new architectures. It was a year until they finally acknowledged the issues. They started getting blasted by tech tubers they ignored the issue to sell their cards. Then they finally started releasing proper collection tools in their drivers. Hopefully with the bug collection tools they won't run into this issue again with which ever architecture replaces RDNA. AMD's GCN drivers were so bad, once AMD figured out how to properly optimize them fanboys started calling it "AMD's Fine Wine." That's why Polaris/Vega weren't gaining any major improvements after years aside from game day drivers.

https://youtu.be/pboDbxogSw4

https://youtu.be/1uynVO4ZXl0

The RX 5000 series came out a year and 2 months before Covid.

Don't know where you are getting the idea I am a fanboy. I run a GTX 1070 and a RX 6600 XT. Intel i7 7th gen and AMD 5800X so I have a mixed bag. You seem to forget that ppl with issues have the loudest mouth and are a minority while the majority of ppl don't have issues whatsoever.

The releasedate was July 7, 2019 and Covid was worldwide februari 2020, if you want to be so pedantic get your facts straight.

Those youtube video's are from jan/feb 2020.

[Melcar]

But how much performance did you lose in going back to a FX-9590? Did you "Before & After" benchmark your changes?

Probably a lot. I used to run a FX8320 @ 4.8GHz before and when I upgraded to a R7 1700 the performance uplift was very noticeable, even with the Ryzen at stock frequencies. Especially for light threaded frequency heavy workloads.