On Tue, 2 Apr 2019, Thomas Gleixner wrote:
> On Tue, 2 Apr 2019, Andy Lutomirski wrote:
> > > On Apr 2, 2019, at 9:48 AM, Thomas Gleixner <t...@linutronix.de> wrote:
> > >
> > >> On Tue, 2 Apr 2019, Josh Poimboeuf wrote:
> > >>> On Tue, Apr 02, 2019 at 12:19:46PM +0200, Thomas Gleixner wrote:
> > >>> +/*
> > >>> + * Array of exception stack page descriptors. If the stack is larger
> > >>> than
> > >>> + * PAGE_SIZE, all pages covering a particular stack will have the same
> > >>> + * info.
> > >>> + */
> > >>> +static const struct estack_pages estack_pages[ESTACK_PAGES]
> > >>> ____cacheline_aligned = {
> > >>> + [CONDRANGE(DF)] = ESTACK_PAGE(DOUBLEFAULT_IST, DF),
> > >>> + [CONDRANGE(NMI)] = ESTACK_PAGE(NMI_IST, NMI),
> > >>> + [PAGERANGE(DB)] = ESTACK_PAGE(DEBUG_IST, DB),
> > >>> + [CONDRANGE(MCE)] = ESTACK_PAGE(MCE_IST, MCE),
> > >>
> > >> It would be nice if the *_IST macro naming aligned with the struct
> > >> cea_exception_stacks field naming. Then you could just do, e.g.
> > >> ESTACKPAGE(DF).
> > >
> > > Yes, lemme fix that up.
> > >
> > >> Also it's a bit unfortunate that some of the stack size knowledge is
> > >> hard-coded here, i.e #DB always being > 1 page and non-#DB being
> > >> sometimes 1 page.
> > >
> > > The problem is that there is no way to make this macro maze conditional on
> > > sizeof(). But my macro foo is rusty.
> >
> > How about a much better fix: make the DB stack be the same size as all
> > the others and just have 4 of them (DB0, DB1, DB2, and DB3. After all,
> > overflowing from one debug stack into another is just as much of a bug as
> > overflowing into a different IST stack.
>
> That makes sense.
Except that we just have two not four.
It needs some tweaking of the ist_shift stuff in entry_64.S but that's not
rocket science. Famous last words....
Thanks,
tglx
