On Fri, May 29, 2020 at 1:26 AM Lai Jiangshan <la...@linux.alibaba.com> wrote: > > 7f2590a110b8("x86/entry/64: Use a per-CPU trampoline stack for IDT entries") > has resulted that when exception on userspace, the kernel (error_entry) > always push the pt_regs to entry stack(sp0), and then copy them to the > kernel stack. > > And recent x86/entry work makes interrupt also use idtentry > and makes all the interrupt code save the pt_regs on the sp0 stack > and then copy it to the thread stack like exception. > > This is hot path (page fault, ipi), such overhead should be avoided. > And the original interrupt_entry directly switches to kernel stack > and pushes pt_regs to kernel stack. We should do it for error_entry. > This is the job of patch1. > > Patch 2-4 simply stack switching for .Lerror_bad_iret by just doing > all the work in one function (fixup_bad_iret()). > > The patch set is based on tip/x86/entry (28447ea41542) (May 20).
There are definitely good cleanups in here, but I think it would be nice rebased to whatever lands in 5.8-rc1 settles. --Andy