7f2590a110b8("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")
made a change that when any exception happens on userspace, the
entry code will save the pt_regs on the sp0 stack, and then copy it
to the thread stack via sync_regs() and switch to thread stack
afterward.This is hot path, such overhead should be avoided. This patch borrows the way how interrupt_entry handles it. Signed-off-by: Lai Jiangshan <[email protected]> --- arch/x86/entry/entry_64.S | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 5e983506f82e..e8817ae31390 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1321,19 +1321,13 @@ SYM_CODE_END(paranoid_exit) SYM_CODE_START_LOCAL(error_entry) UNWIND_HINT_FUNC cld - PUSH_AND_CLEAR_REGS save_ret=1 - ENCODE_FRAME_POINTER 8 - testb $3, CS+8(%rsp) + testb $3, CS-ORIG_RAX+8(%rsp) jz .Lerror_kernelspace - /* - * We entered from user mode or we're pretending to have entered - * from user mode due to an IRET fault. - */ - SWAPGS - FENCE_SWAPGS_USER_ENTRY - /* We have user CR3. Change to kernel CR3. */ - SWITCH_TO_KERNEL_CR3 scratch_reg=%rax + idtentry_swapgs_and_switch_to_kernel_stack + PUSH_AND_CLEAR_REGS save_ret=1 + ENCODE_FRAME_POINTER 8 + ret .Lerror_entry_from_usermode_after_swapgs: /* Put us onto the real thread stack. */ @@ -1357,6 +1351,8 @@ SYM_CODE_START_LOCAL(error_entry) * for these here too. */ .Lerror_kernelspace: + PUSH_AND_CLEAR_REGS save_ret=1 + ENCODE_FRAME_POINTER 8 leaq native_irq_return_iret(%rip), %rcx cmpq %rcx, RIP+8(%rsp) je .Lerror_bad_iret -- 2.20.1
