On 06/28/2012 02:30 PM, Peter Zijlstra wrote: > On Thu, 2012-06-28 at 13:19 +0200, Martin Schwidefsky wrote: > >> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>