On Mon, Nov 27, 2017 at 06:33:39PM +0100, Thomas Gleixner wrote: > On Mon, 27 Nov 2017, Peter Zijlstra wrote: > > On Mon, Nov 27, 2017 at 11:49:01AM +0100, Ingo Molnar wrote: > > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > > > index caf74a1bb3de..df0152bee8a8 100644 > > > > > @@ -198,6 +201,14 @@ ENTRY(entry_SYSCALL_64) > > > > > > swapgs > > > movq %rsp, PER_CPU_VAR(rsp_scratch) > > > + > > > + /* > > > + * The kernel CR3 is needed to map the process stack, but we > > > + * need a scratch register to be able to load CR3. %rsp is > > > + * clobberable right now, so use it as a scratch register. > > > + * %rsp will look crazy here for a couple instructions. > > > + */ > > > + SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp > > > movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp > > > > > > /* Construct struct pt_regs on stack */ > > > > I think we can do away with this one, on account of never getting here > > because of entry_SYSCALL_64_trampoline. > > It's on my list already. About 5 people noticed :)
Hey, at least we all agree ;-)
