On Mon, Jun 15, 2020 at 11:12:59AM -0700, Fenghua Yu wrote: > > I don't get why you need a rdmsr here, or why not having one would > > require a TIF flag. Is that because this MSR is XSAVE/XRSTOR managed? > > My concern is TIF flags are precious (only 3 slots available). Defining > a new TIF flag may be not worth it while rdmsr() can check if PASID > is valid in the MSR. And performance here might not be a big issue > in #GP. > > But if you think using TIF flag is better, I can define a new TIF flag > and maintain it per thread (init 0 when clone()/fork(), set 1 in fixup()). > Then we can avoid using rdmsr() to check valid PASID in the MSR.
WHY ?!?! What do you need a TIF flag for?