[Info-vax] Intel junk...Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign

[Jan-Erik Soderholm]

Den 2018-01-04 kl. 23:04, skrev Tim Streater:
> In article <p2m3kt$vnk$1 at dont-email.me>, DaveFroble
> <davef at tsoft-inc.com> wrote:
> 
>> chrisv wrote:
>>> Designed By India H1B Engineers wrote:
>>>
>>>> Crucially, these updates to both Linux and Windows will incur a 
>>>> performance hit on Intel products. The effects are still being 
>>>> benchmarked, however we're looking at a ballpark figure of five to 30 
>>>> per cent slow down, depending on the task and the processor model.
>>>
>>> This is ugly.  Think of the large computing centers, for example
>>> Google's data centers.  Suddenly, they will need significantly more
>>> CPU time, and thus electricity (and thus carbon), to get the job done?
>>>
>>
>> And once all the spanners are tossed into the works, which will slow 
>> things down, what happens when new CPUs without the issues are 
>> available?  Will computers forever be artificially slowed down?
>>
>> A whole bunch of someones has seriously dropped the ball on this.  
>> Protected memory should be just that, protected, with no way to avoid the 
>> protection.
> 
> But AIUI, the protection isn't applied when the CPU does speculative
> instruction execution. It's unclear why, though.
> 

Becuse the designers, for performance reasons, has mapped kernel memory
into the user process address space and relies on the OS to check
protection before any kernel memory (or code) is accessed.

The issue with the current issues is that the hardware (the CPU) does
these accesses in hardware "under the hood" without control by the OS.

If you map your kernel memory in another way that uses the hardware
protection facilities, you are (as I understand) safe, at the cost
of worse performance to switch between user and kernel mode.