AMD claims their processors aren't affected at all by any of the 3 variants of Foreshadow (https://www.amd.com/en/corporate/security-updates) therefore SMT is safe to leave enabled. On the other hand, on Intel the only fully comprehensive workaround is to completely disable SMT, so given that disabling SMT almost halves the performance on some workloads,¹ AMD is bound to have a huge performance advantage over Intel, on these particular workloads.
¹ For example in SPECvirt_sc2013 the patch reduces performance by 31% (https://www.servethehome.com/wp-content/uploads/2018/08/Inte...) 31% is unheard of for a security patch! It's a difficult security-speed tradeoff that businesses must carefully consider.
Should truth-in-advertising laws require OEMs to stop advertising hyper-threading, e.g. 4C/8T on new hardware, if the advertised feature is not fit for purpose?
I believe it may be because the email only mentioned Intel explicitly and had a "I won't be buying Intel in future" (paraphrased) comment. However, I personally wouldn't assume that AMDs HT implementation doesn't have similar issues.
> However, I personally wouldn't assume that AMDs HT implementation doesn't have similar issues.
It does not. The fundamental difference between AMD and Intel CPUs in all these faults is that AMD does all permissions checks eagerly before returning results from memory, while when speculating, Intel defers them until speculation is resolved.
This does not mean that AMD escaped all of it, because some of the attacks (eg, spectre variant 1) do not cross a protection boundary that permissions checks would catch.
Where did you get that impression?
AMD claims their processors aren't affected at all by any of the 3 variants of Foreshadow (https://www.amd.com/en/corporate/security-updates) therefore SMT is safe to leave enabled. On the other hand, on Intel the only fully comprehensive workaround is to completely disable SMT, so given that disabling SMT almost halves the performance on some workloads,¹ AMD is bound to have a huge performance advantage over Intel, on these particular workloads.
¹ For example in SPECvirt_sc2013 the patch reduces performance by 31% (https://www.servethehome.com/wp-content/uploads/2018/08/Inte...) 31% is unheard of for a security patch! It's a difficult security-speed tradeoff that businesses must carefully consider.
Should truth-in-advertising laws require OEMs to stop advertising hyper-threading, e.g. 4C/8T on new hardware, if the advertised feature is not fit for purpose?
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I believe it may be because the email only mentioned Intel explicitly and had a "I won't be buying Intel in future" (paraphrased) comment. However, I personally wouldn't assume that AMDs HT implementation doesn't have similar issues.
> However, I personally wouldn't assume that AMDs HT implementation doesn't have similar issues.
It does not. The fundamental difference between AMD and Intel CPUs in all these faults is that AMD does all permissions checks eagerly before returning results from memory, while when speculating, Intel defers them until speculation is resolved.
This does not mean that AMD escaped all of it, because some of the attacks (eg, spectre variant 1) do not cross a protection boundary that permissions checks would catch.
HT is also disabled on AMD, for both CMT (FPU-shared) & SMT implementations.
https://marc.info/?l=openbsd-cvs&m=152954666609919&w=2
While no AMD issues are known at present. OpenBSD will have it disabled by default. How about other operating systems, I wonder?
Possibly, but it's not uncommon to refer to x86 and x64 machines as intel architecture machines or as intel machines.
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