On Mon, 20 Nov 2017, Andy Lutomirski wrote: > This will simplify future changes that want scratch variables early in > the SYSENTER handler -- they'll be able to spill registers to the > stack. It also lets us get rid of a SWAPGS_UNSAFE_STACK user. > > This does not depend on CONFIG_IA32_EMULATION because we'll want the > stack space even without IA32 emulation. > > As far as I can tell, the reason that this wasn't done from day 1 is > that we use IST for #DB and #BP, which is IMO rather nasty and causes > a lot more problems than it solves. But, since #DB uses IST, we don't > actually need a real stack for SYSENTER (because SYSENTER with TF set > will invoke #DB on the IST stack rather than the SYSENTER stack). > I want to remove IST usage from these vectors some day, and this patch > is a prerequisite for that as well. > > Signed-off-by: Andy Lutomirski <l...@kernel.org>
Reviewed-by: Thomas Gleixner <t...@linutronix.de>
