On 11/01/2017 01:54 AM, Ingo Molnar wrote: > Beyond the inevitable cavalcade of (solvable) problems that will pop up > during > review, one major item I'd like to see addressed is runtime configurability: > it > should be possible to switch between a CR3-flushing and a regular syscall and > page > table model on the admin level, without restarting the kernel and apps. > Distros > really, really don't want to double the number of kernel variants they have. > > The 'Kaiser off' runtime switch doesn't have to be as efficient as > CONFIG_KAISER=n, at least initialloy, but at minimum it should avoid the most > expensive page table switching paths in the syscall entry codepaths.
Due to popular demand, I went and implemented this today. It's not the prettiest code I ever wrote, but it's pretty small. Just in case anyone wants to play with it, I threw a snapshot of it up here: > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-kaiser.git/log/?h=kaiser-dynamic-414rc6-20171101 I ran some quick tests. When CONFIG_KAISER=y, but "echo 0 > kaiser-enabled", the tests that I ran were within the noise vs. a vanilla kernel, and that's with *zero* optimization.
