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AMD silently removes memory encryption from consumer Ryzen CPUs

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31–40 of 225 posts

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#31
post #19

For what it's worth, RAM encryption belongs to professional SKUs. It's the right business decision that should have been made from from the very beginning. For most consumer users, RAM encryption primarily adds power consumption and heat generation while providing little practical benefit. They simply don't face many of the threat vectors and attack scenarios that certain industries and enterprise environments must c…

how do you know what threats I face? how do you know what threats journalists and whistleblowers face? this is approximately the same discussion as with ECC RAM: the benefits vastly outweigh the slight performance loss and die area increases.

ECC passively benefits everyone, even people who don't know what it is or why it's useful. Anyone can be a victim of random bit flips, it's not a targeted threat.

Memory encryption, on the other hand, provides absolutely no benefit to 99.999% of users. If you consider yourself to be such a high value target that you suspect someone might gain physical access to your hardware without your knowledge and carry out extremely sophisticated hardware attacks to extract your data, you are a tiny minority and it makes sense that such niche protections would require buying specialized hardware. Even then, the odds of such an attack being chosen instead of a far less sophisticated software-based approach are also tiny.

Of course, if the hardware itself supports the feature and AMD simply decided to disable it, that's still a shitty thing to do, but let's not pretend that it is in any way comparable to ECC.

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#32
post #28
post #22

It's a shame there is no software-based memory encryption included in the linux kernel. Especially cloud providers can easily snoop all your keys and you have zero recourse.

There was a patch called Tresor that did this, but I don't think it was updated for a long time. You have to store the encryption key in CPU registers and ensure it's not saved to RAM during task switching or power suspend operations. Tresor used x86-specific debug registers for it, but you could potentially use unused SIMD registers if you masked-off the CPUID bits for them and disabled them for access by user-space…

> You have to store the encryption key in CPU registers and ensure it's not saved to RAM during task switching or power suspend operations.

Interesting insight. Any reason why the key can't be kept exclusively in the secure enclave / trusted platform module / crypto coprocessor?

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#33
post #26

Earlier quoted context omitted.

Sneakily and silently removing a feature in a firmware revision is not acceptable, security or otherwise.

if anyone does it sneakily, there is alleged wrongdoing attached to it. I can imagine multiple scenarios like some well-known Israeli company "selling their software only to governments", paying quite amount of money for it, because they were unable to break this one.

> there is alleged wrongdoing attached to it

Probably not from a legal perspective, but morally yes. Apple cause batterygate with good intentions but sneakily. Not being transparent is what shot them in the foot. AMD didn't learn anything or thinks this is small-time so no blowback (sadly they might be right).

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#34
post #23

Earlier quoted context omitted.

How can manufacturers simultaneously have exceptional control over flags and not enough control to know what flags are enabled on their shipping products? They either have that control or they don't.

You choose every piece of food you eat, how do you not know all the macros?

This analogy holds true if I invented every molecule in my food.

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#35
I wonder what the additional power draw of these features would be. Parenthetically, I wonder often about the energy impact of all these HTTPS localhost links, and is there a point where defense-in-depth has to give way to other concerns?

But yeah 95% of the consumer market don't care about this and it's only adding unnecessary costs

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#36
post #9

Earlier quoted context omitted.

How can manufacturers simultaneously have exceptional control over flags and not enough control to know what flags are enabled on their shipping products? They either have that control or they don't.

They always had control. Awareness is a different thing. You could just as well ask "if you've written every line of code, why did you write that bug?".

I'm trying to progress the discussion past "we don't know if it was intentional". We know it was intentional. What was the intention of having it on before and what is the intention of turning it off?

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#37
post #5

Earlier quoted context omitted.

> To be fair to AMD, there is no clear indication that the company ever publicly advertised TSME as a consumer Ryzen feature. A feature that was possibly accidentally enabled on consumer chips is now being disabled. I would guess that the number of owners of consumer chips who also relied on them for encryption is exceedingly small. The primary concern persists. The manufacturer has an exceptional amount of control o…

How can manufacturers simultaneously have exceptional control over flags and not enough control to know what flags are enabled on their shipping products? They either have that control or they don't.

AMD, historically, has taken a "we don't test enterprise features on consumer SKUs, but we don't fuse them off if you really want to qualify it or let them try it" approach to e.g. ECC on consumer chips with Zen.

So it's quite possible they were doing the same with TSME, and either made a rude marketing decision that the people using it on consumer chips would probably pay for PRO chips if they were prevented from doing so, or kept getting people attempting to RMA the chips for a feature they never said worked on them not working, or there's some systemic flaw in the consumer chip's implementation that they didn't feel like trying to qualify fixing versus just killing the not-guaranteed support.

Hard to guess without more data than just them going silent about it.

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#39
post #5

Earlier quoted context omitted.

> To be fair to AMD, there is no clear indication that the company ever publicly advertised TSME as a consumer Ryzen feature. A feature that was possibly accidentally enabled on consumer chips is now being disabled. I would guess that the number of owners of consumer chips who also relied on them for encryption is exceedingly small. The primary concern persists. The manufacturer has an exceptional amount of control o…

How can manufacturers simultaneously have exceptional control over flags and not enough control to know what flags are enabled on their shipping products? They either have that control or they don't.

AMD has limited control over what motherboard manufacturers do. And there have been plenty of examples demonstrating motherboard vendors don't fully understand what they are doing. Stuff like shipping builds with example/placeholder keys, ridiculous voltage settings which destroy the cpu. Even if motherboard vendors don't have full control to configure to freely change every flag, they probably have access to some kind of debug/development firmware which has a lot more features enabled than what you would have in consumer builds.

Re: AMD silently removes memory encryption from consumer Ryzen CPUs

#40
post #5
post #2

Any idea what's happening? This sounds _bad_.

> To be fair to AMD, there is no clear indication that the company ever publicly advertised TSME as a consumer Ryzen feature. A feature that was possibly accidentally enabled on consumer chips is now being disabled. I would guess that the number of owners of consumer chips who also relied on them for encryption is exceedingly small. The primary concern persists. The manufacturer has an exceptional amount of control o…

> I would guess that the number of owners of consumer chips who also relied on them for encryption is exceedingly small.

I guarantee you that there's one small company that put 1,000 of these chips in a server room or datacentre though, and they're now completely boned.

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