On Fri, Jun 30, 2017 at 08:56:09AM -0700, Andy Lutomirski wrote: > On Fri, Jun 30, 2017 at 8:55 AM, Josh Poimboeuf <jpoim...@redhat.com> wrote: > > On Fri, Jun 30, 2017 at 08:44:40AM -0700, Andy Lutomirski wrote: > >> > A few comments about the first patch: > >> > > >> > > >> > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=3e2aa2102cc1c5e60d4a8637bff78d0478a55059 > >> > > >> > - It uses a '693:' label instead of '.Lirqs_off_\@:' > >> > >> Touché! > >> > >> > > >> > - There's a comment I don't follow: > >> > > >> > "Anything that can interrupt us here without using IST must be > >> > *extremely* careful to limit its stack usage." > >> > > >> > What specifically could interrupt there without using IST? > >> > >> #DB, later on in the series. I'll update the comment. > >> > >> > > >> > - Since do_softirq_own_stack() is a callable function, I think it still > >> > needs to save rbp. > >> > >> Whoops. > >> > >> > > >> > - Why change the "jmp error_exit" to "ret" in > >> > xen_do_hypervisor_callback()? > >> > >> To match the other change I made there. I removed both. > > > > One more thing I forgot to mention: if you could use r10 instead of r11, > > that would be helpful because it means one less register undwarf needs > > to know about. (It already deals with r10 because of GCC stack > > realignment). > > I'll let you figure that one out :) > > (Although I think I agree with hpa: why not let it support all regs? > Or am I missing something still?)
Sure, it can support all regs, but as the code is structured now, doing so means adding more switch cases, e.g.: https://github.com/jpoimboe/linux/blob/undwarf-v2/arch/x86/kernel/unwind_undwarf.c#L388 And that makes the balrog angry! -- Josh
