On Mon, Nov 27, 2017 at 02:47:08PM -0800, Dave Hansen wrote: > On 11/27/2017 02:31 PM, Peter Zijlstra wrote: > > We never use this code-path with KAISER enabled. > ... > > @@ -201,14 +201,6 @@ 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 > > What's the mechanism that we use to switch between the two versions of > the SYSCALL entry? It wasn't obvious from some grepping.
the next patch, the code in tip will in fact never use this code.
