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.
