The worst part of this exploit is all the people exploiting it to gain attention for themselves, like with ridiculous comments such as this. As if engineers were actually told to ignore risk. What a crock of shit.
To quote Linus "A *competent* CPU engineer would fix this by making sure speculation doesn't happen across protection domains." It's pretty bleeding obvious that either the Intel engineers are completely incompetent,orthey were instructed to look the other way.
There are no other alternatives. Linus says so, and now Theo too. Who are you, oh mighty commenter who knows better?
To quote Linus "A *competent* CPU engineer would fix this by making sure speculation doesn't happen across protection domains."
That's bullshit. When Intel introduced speculation across protection domains everyone including Linux was happy because it reduced system call costs. Without this, as soon as you get to a syscall / sysenter instruction, you stall the pipeline until all pending instructions have been committed. On a modern Intel CPU with close to 200 instructions in flight at a time, that's a measurable performance overhead.
We've known for a long time that side channels of this kind were possible, but not that they were
Bullshit you say, and yet it's only Intel and a few, comparatively insignificant ARM chips which are affected by meltdown, which btw, was what Linus was referring to.
I can only presume AMD is an imaginary entity in your little world, because they apparently managed to solve all these impossible problems without handing out the keys to the kingdom to everyone who asked for them.
Bullshit you say, and yet it's only Intel and a few, comparatively insignificant ARM chips which are affected by meltdown, which btw, was what Linus was referring to.
Ye, because Intel patented the technique and didn't license it to anyone else.
I can only presume AMD is an imaginary entity in your little world, because they apparently managed to solve all these impossible problems without handing out the keys to the kingdom to everyone who asked for them.
Nope, AMD pays a higher penalty on system calls, though they mitigate this to some extent by having shorter and narrower pipelines.
Nope, AMD pays a higher penalty on system calls, though they mitigate this to some extent by having shorter and narrower pipelines.
How is that? Checking for permissions before speculation costs hardware and power but not speculating a path which is not going to be used anyway is hardly going to increase latency and saves the power which would otherwise be used and the cost of any memory transactions.
System calls involve a lot of microcode and other functions so it is not surprising they have a high and different cost between processors.
"I bet they were instructed to ignore the risk" (Score:-1)
Re: (Score:0)
Crock of shit, you mean like your own comment?
To quote Linus "A *competent* CPU engineer would fix this by making sure speculation doesn't happen across protection domains." It's pretty bleeding obvious that either the Intel engineers are completely incompetent, or they were instructed to look the other way.
There are no other alternatives. Linus says so, and now Theo too. Who are you, oh mighty commenter who knows better?
Re: (Score:5, Interesting)
To quote Linus "A *competent* CPU engineer would fix this by making sure speculation doesn't happen across protection domains."
That's bullshit. When Intel introduced speculation across protection domains everyone including Linux was happy because it reduced system call costs. Without this, as soon as you get to a syscall / sysenter instruction, you stall the pipeline until all pending instructions have been committed. On a modern Intel CPU with close to 200 instructions in flight at a time, that's a measurable performance overhead.
We've known for a long time that side channels of this kind were possible, but not that they were
Re: (Score:0)
Bullshit you say, and yet it's only Intel and a few, comparatively insignificant ARM chips which are affected by meltdown, which btw, was what Linus was referring to.
I can only presume AMD is an imaginary entity in your little world, because they apparently managed to solve all these impossible problems without handing out the keys to the kingdom to everyone who asked for them.
Bullshit, yeah, plenty of that in your post.
Re: (Score:4, Informative)
Bullshit you say, and yet it's only Intel and a few, comparatively insignificant ARM chips which are affected by meltdown, which btw, was what Linus was referring to.
Ye, because Intel patented the technique and didn't license it to anyone else.
I can only presume AMD is an imaginary entity in your little world, because they apparently managed to solve all these impossible problems without handing out the keys to the kingdom to everyone who asked for them.
Nope, AMD pays a higher penalty on system calls, though they mitigate this to some extent by having shorter and narrower pipelines.
Re:"I bet they were instructed to ignore the risk" (Score:2)
Nope, AMD pays a higher penalty on system calls, though they mitigate this to some extent by having shorter and narrower pipelines.
How is that? Checking for permissions before speculation costs hardware and power but not speculating a path which is not going to be used anyway is hardly going to increase latency and saves the power which would otherwise be used and the cost of any memory transactions.
System calls involve a lot of microcode and other functions so it is not surprising they have a high and different cost between processors.