On 06/28/2012 02:30 PM, Peter Zijlstra wrote:

On Thu, 2012-06-28 at 13:19 +0200, Martin Schwidefsky wrote:

quoted

The cpu can create speculative TLB entries, but only if it runs in the
mode that uses the respective mm. We have two mm's active at the same
time, the kernel mm (init_mm) and the user mm. While the cpu runs only
in kernel mode it is not allowed to create TLBs for the user mm.
While running in user mode it is allowed to speculatively create TLBs.

OK, that's neat.

Note that we can do that for x86 now using the new PCID feature.
Basically you get a tagged TLB, so you can switch between the
kernel-only address space and the kernel+user address space quickly.

It's still going to be slower than what we do now, but it might please
some security people if the kernel can't accidentally access user data.

-- 
error compiling committee.c: too many arguments to function


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