On Wed, Nov 1, 2017 at 10:25 AM, Brian Gerst <brge...@gmail.com> wrote: > On Thu, Oct 26, 2017 at 4:26 AM, Andy Lutomirski <l...@kernel.org> wrote: >> They did almost the same thing. Remove a bunch of pointless >> instructions (mostly hidden in macros) and reduce cognitive load by >> merging them. >> >> Signed-off-by: Andy Lutomirski <l...@kernel.org> >> --- >> arch/x86/entry/entry_64.S | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S >> index 9dafafa3e0ec..c855ee91a3a5 100644 >> --- a/arch/x86/entry/entry_64.S >> +++ b/arch/x86/entry/entry_64.S >> @@ -220,10 +220,9 @@ entry_SYSCALL_64_fastpath: >> TRACE_IRQS_ON /* user mode is traced as IRQs on */ >> movq RIP(%rsp), %rcx >> movq EFLAGS(%rsp), %r11 >> - RESTORE_C_REGS_EXCEPT_RCX_R11 >> - movq RSP(%rsp), %rsp >> + addq $6*8, %rsp /* skip extra regs -- they were preserved */ >> UNWIND_HINT_EMPTY >> - USERGS_SYSRET64 >> + jmp .Lpop_c_regs_except_rcx_r11_and_sysret >> >> 1: >> /* >> @@ -315,6 +314,7 @@ syscall_return_via_sysret: >> /* rcx and r11 are already restored (see code above) */ >> UNWIND_HINT_EMPTY >> POP_EXTRA_REGS >> +.Lpop_c_regs_except_rcx_r11_and_sysret: >> popq %rsi /* skip r11 */ >> popq %r10 >> popq %r9 > > Wouldn't it be more logical to keep the SYSRET path at the end of the > fast path (reverse of what you are doing here)? That way the fast > path falls through without jumping.
Ugh, probably. I think I'll save that for v3, though. I want to keep this moving.
