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No, it works with multiple CPUs, multiple address spaces and multithreading.

Combuster wrote:

jal wrote:but that means the scheduler must update the MSR when switching tasks.

Not necessarily. You can just have it contain a pointer to a valid temporary stack, then update ESP manually. (instead of finding out the value for ESP, then bothering the slow WRMSR with it)

Indeed. Thanks for pointing it out.


JAL

The convention with syscall/sysret is to use the SWAPGS instruction and hang a "processor control block" off of the kernel's GS.

For this reason, I'm looking forward to clang & llvm maturing, because they have support for declaring a pointer off the GS segment, and therefore better optimized code.