Re: Per-cpu IDT patch

[s ymgch <s.ymgch228%gmail.com@localhost>]

On Fri, Jul 3, 2020 at 3:27 PM Maxime Villard <max%m00nbsd.net@localhost> wrote:
>
> Le 03/07/2020 à 07:11, s ymgch a écrit :
> > Hi all,
> >
> > I tried to make an IDT per-cpu. The patch is here:
> > http://www.netbsd.org/~yamaguchi/pcpu-idt.patch
> >
> > The summary of modifications is as follows.
> > - Add an IDT pointer and idt_allocmap into struct cpu_info
> > - Change prototype of cpu_init_idt()
> >     - void => struct cpu_info*
> >     - for loading an IDT address in struct cpu_info*
> > - Copy a part of IDT entries from cpu 0 at attaching a CPU
> >     - for the same entries, for example, exceptions, db, etc.
> >
> > This function can be enabled by PCPU_IDT option that is newly provided.
>
> Why would we want a per-cpu IDT? To increase the number of entries?

Yes, the intent of the patch is to increase the number of entries.
There was a report about lack of the entries:
http://gnats.netbsd.org/54837

>
> > Does this patch look good?
> > Please let me know if you have any comments about this.
>
> Since the idt page is moved into pcpu_entry, it can be removed from
> pcpu_area

I will change it.