Re: [PATCH V2 0/4] x86/entry: simply stack switching when exception on userspace

[Lai Jiangshan]

Hello and Ping

On Tue, Jun 16, 2020 at 9:56 AM Lai Jiangshan
<jiangshanlai+lkml@xxxxxxxxx> wrote:
>
> On Sat, May 30, 2020 at 2:33 AM Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> >
> > On Fri, May 29, 2020 at 1:26 AM Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> 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.

Ping Andy Lutomirski for having added the overhead two years ago.

> > >
> > > 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.
> > >

Ping Thomas Gleixner for having added the overhead recently.

>
> Hello, All
>
> This patchset can be smoothly applicable to the newest tip/x86/entry
> which has 5.8-rc1 merged. Which means I don't have to respin/resend it
> until any update is needed.
>
> Could you have a review on it please.
>
> Thanks
> Lai