The problem(s) with it were that it was underspecified _how_ negative the workload impacts were for some cases, and that it ended up in stable branches default-on before getting reverted for the impact.
As Linus remarked in the thread, the people who were paranoid about the security implications already went the BSD route and disabled SMT, while the people who don't worry about it that much suddenly get a nasty perf impact by default.
To quote an Intel rep in the thread:
"Using these tools much more surgically is fine, if a paranoid task wants it for example,
or when you know you are doing a hard core security transition. But always on? Yikes."
Yes, your system should default to being secure. But there's a sliding scale when deciding on security flaw mitigations of user disruption versus level of security given.
In this case, the user disruption was medium-high, and the benefits did not outweigh that, so the intersection of the two factors was refined.
If this were something every skiddy toolkit were leveraging to exfiltrate astonishing amounts of data, this might fall the other way. But right now, that's not where we are.
As Linus remarked in the thread, the people who were paranoid about the security implications already went the BSD route and disabled SMT, while the people who don't worry about it that much suddenly get a nasty perf impact by default.
To quote an Intel rep in the thread: "Using these tools much more surgically is fine, if a paranoid task wants it for example, or when you know you are doing a hard core security transition. But always on? Yikes."
Yes, your system should default to being secure. But there's a sliding scale when deciding on security flaw mitigations of user disruption versus level of security given.
In this case, the user disruption was medium-high, and the benefits did not outweigh that, so the intersection of the two factors was refined.
If this were something every skiddy toolkit were leveraging to exfiltrate astonishing amounts of data, this might fall the other way. But right now, that's not where we are.